THE FOUNDATIONS OF THE ORIGIN OF
SPECIES

Astronomers might formerly have said that God ordered each
planet to
move in its particular destiny. In same manner God orders each animal
created with certain form in certain country. But how much more simple
and sublime power,—let attraction act according to certain law, such
are inevitable consequences,—let animal<s> be created, then by the
fixed laws of generation, such will be their successors.

ON THE VARIATION OF ORGANIC BEINGS UNDER
DOMESTICATION; AND ON THE PRINCIPLES OF SELECTION.

Variation—On the hereditary tendency—Causes of
Variation—On
Selection—Crossing Breeds—Whether our domestic races have descended
from one or more wild stocks—Limits to Variation in degree and kind—In
what consists Domestication—Summary . . 57-80

CHAPTER
II

ON THE VARIATION OF ORGANIC BEINGS IN A
WILD STATE;
ON THE NATURAL MEANS OF SELECTION; AND ON THE COMPARISON OF DOMESTIC
RACES AND TRUE SPECIES.

Variation—Natural means of Selection—Differences between
"Races" and
"Species":—first, in their trueness or variability—Difference between
"Races" and "Species" in fertility when crossed—Causes of Sterility in
Hybrids—Infertility from causes distinct from hybridisation—Points of
Resemblance between "Races" and "Species"—External characters of
Hybrids and Mongrels—Summary—Limits of Variation 81-111

CHAPTER
III

ON THE VARIATION OF INSTINCTS AND OTHER
MENTAL
ATTRIBUTES UNDER DOMESTICATION AND IN A STATE OF NATURE; ON THE
DIFFICULTIES IN THIS SUBJECT; AND ON ANALOGOUS DIFFICULTIES WITH
RESPECT TO CORPOREAL STRUCTURES.

Variation of mental attributes under
domestication—Hereditary habits
compared with instincts—Variation in the mental attributes of wild
animals—Principles of Selection applicable to instincts—Difficulties in
the acquirement of complex instincts by Selection—Difficulties in the
acquirement by Selection of complex corporeal structures . 112-132

ON THE EVIDENCE FAVOURABLE AND OPPOSED TO
THE VIEW
THAT SPECIES ARE NATURALLY FORMED RACES, DESCENDED FROM COMMON STOCKS.

CHAPTER
IV

ON THE NUMBER OF INTERMEDIATE
FORMS
REQUIRED ON THE THEORY OF COMMON DESCENT; AND ON THEIR ABSENCE IN A
FOSSIL STATE ....... 133-143

CHAPTER
V

GRADUAL APPEARANCE AND
DISAPPEARANCE OF
SPECIES.

Gradual appearance of species—Extinction of species . .
144-150

CHAPTER
VI

ON THE GEOGRAPHICAL DISTRIBUTION OF ORGANIC
BEINGS IN
PAST AND PRESENT TIMES.

SECTION FIRST

Distribution of the inhabitants in the different
continents—Relation
of range in genera and species—Distribution of the inhabitants in the
same continent—Insular Faunas—Alpine Floras—Cause of the similarity in
the floras of some distant mountains—Whether the same species has been
created more than once—On the number of species, and of the classes to
which they belong in different regions 151-174

SECOND SECTION

Geographical distribution of extinct organisms—Changes in
geographical distribution—Summary on the distribution of living and
extinct organic beings ......... 174-182

SECTION THIRD

An attempt to explain the foregoing laws of geographical
distribution, on the theory of allied species having a common
descent—Improbability of finding fossil forms intermediate between
existing species 183-197

CHAPTER
VII

ON THE NATURE OF THE AFFINITIES AND
CLASSIFICATION OF
ORGANIC BEINGS.

Gradual appearance and disappearance of groups—What is the
Natural
System?—On the kind of relation between distinct groups—Classification
of Races or Varieties—Classification of Races and Species
similar—Origin of genera and families .... 198-213

Unity of Type—Morphology—Embryology—Attempt to explain the
facts of
embryology—On the graduated complexity in each great class—Modification
by selection of the forms of immature animals—Importance
of embryology in classification—Order in time in which the great
classes have first appeared ....... 214-230

WE know from the contents of Charles Darwin's Note Book of
1837 that
he was at that time a convinced Evolutionist1. Nor can there
be any doubt that, when he started on board the Beagle, such
opinions as he had were on the side of immutability. When therefore did
the current of his thoughts begin to set in the direction of Evolution?

We have first to consider the factors that made for such a
change.
On his departure in 1831, Henslow gave him vol. I. of
Lyell's Principles,
then just published, with the warning that he was not to believe what
he read2. But believe he did, and it is certain (as Huxley
has forcibly pointed out3) that the doctrine of
uniformitarianism when applied to Biology leads of necessity to
Evolution. If the extermination of a species is no more catastrophic
than the natural death of an individual, why should the birth of a
species be any more miraculous than the birth of an individual? It is
quite clear that this thought was vividly present to Darwin when he was
writing out his early thoughts in the 1837 Note Book4:—

" Propagation explains why modern animals same type as
extinct, which is law almost proved.

1 See the extracts in Life
and
Letters of Charles Darwin, ii. p. 5.

2 The second volume,—especially
important
in regard to Evolution,— reached him in the autumn of 1832, as Prof.
Judd has pointed out in his most interesting paper in Darwin and
Modern Science. Cambridge, 1909.

They die, without they change, like golden pippins; it is
a generation
of species like generation of individuals."

"If species generate other species their
race
is not utterly cut off."

These quotations show that he was struggling to see in the
origin of
species a process just as scientifically comprehensible as the birth of
individuals. They show, I think, that he recognised the two things not
merely as similar but as identical.

It is impossible to know how soon the ferment of
uniformitarianism
began to work, but it is fair to suspect that in 1832 he had already
begun to see that mutability was the logical conclusion of Lyell's
doctrine, though this was not acknowledged by Lyell himself.

There were however other factors of change. In his
Autobiography1 he wrote:—"During the voyage of the Beagle I had been deeply
impressed by discovering in the Pampean formation great fossil animals
covered with armour like that on the existing armadillos; secondly, by
the manner in which closely allied animals replace one another in
proceeding southward over the Continent; and thirdly, by the South
American character of most of the productions of the Galapagos
archipelago, and more especially by the manner in which they differ
slightly on each island of the group; none of the islands appearing to
be very ancient in a geological sense. It was evident that such facts
as these, as well as many others, could only be explained on the
supposition that species gradually become modified; and the subject
haunted me."

Again we have to ask: how soon did any of these influences
produce
an effect on Darwin's mind? Different answers have been attempted.
Huxley2 held that these facts could not have produced their
essential effect until the voyage had

come to an end, and the "relations of the existing with
the extinct
species and of the species of the different geographical areas with one
another were determined with some exactness." He does not therefore
allow that any appreciable advance towards evolution was made during
the actual voyage of the Beagle.

Professor Judd1 takes a very different view. He
holds
that November 1832 may be given with some confidence as the "date at
which Darwin commenced that long series of observations and reasonings
which eventually culminated in the preparation of the Origin of
Species."

Though I think these words suggest a more direct and
continuous
march than really existed between fossil-collecting in 1832 and writing
the Origin of Species in 1859, yet I hold that it was during
the voyage that Darwin's mind began to be turned in the direction of
Evolution, and I am therefore in essential agreement with Prof. Judd,
although I lay more stress than he does on the latter part of the
voyage.

Let us for a moment confine our attention to the passage,
above
quoted, from the Autobiography and to what is said in the Introduction
to the Origin, Ed. i., viz. "When on board H.M.S. 'Beagle,'
as naturalist, I was much struck with certain facts in the distribution
of the inhabitants of South America, and in the geological relations of
the present to the past inhabitants of that continent." These words,
occurring where they do, can only mean one thing,—namely that the facts
suggested an evolutionary interpretation. And this being so it must be
true that his thoughts began to flow in the direction of Descent at
this early date.

I am inclined to think that the "new light which was
rising in his
mind2" had not yet attained any

effective degree of steadiness or brightness. I think so
because in
his Pocket Book under the date 1837 he wrote, "In July opened first
note-book on 'transmutation of species.' Had been greatly struck from
about month of previous March1 on character of South
American fossils, and species on Galapagos Archipelago. These facts
origin (especially latter), of all my views." But he did not
visit the Galapagos till 1835 and I therefore find it hard to believe
that his evolutionary views attained any strength or permanence until
at any rate quite late in the voyage. The Galapagos facts are strongly
against Huxley's view, for Darwin's attention was "thoroughly aroused2"
by comparing the birds shot by himself and by others on board. The case
must have struck him at once,—without waiting for accurate
determinations,—as a microcosm of evolution.

It is also to be noted, in regard to the remains of
extinct animals,
that, in the above quotation from his Pocket Book, he speaks of March
1837 as the time at which he began to be "greatly struck on character
of South American fossils," which suggests at least that the impression
made in 1832 required reinforcement before a really powerful effect was
produced.

We may therefore conclude, I think, that the evolutionary
current in
my father's thoughts had continued to increase in force from 1832
onwards, being especially reinforced at the Galapagos in 1835 and again
in 1837 when he was overhauling the results, mental and material, of
his travels. And that when the above record in the Pocket Book was made
he unconsciously minimised the earlier beginnings of his theorisings,
and laid more stress on the recent thoughts which were

naturally more vivid to him. In his letter1 to
Otto
Zacharias (1877) he wrote, "On my return home in the autumn of 1836, I
immediately began to prepare my Journal for publication, and then saw
how many facts indicated the common descent of species." This again is
evidence in favour of the view that the later growths of his theory
were the essentially important parts of its development.

In the same letter to Zacharias he says, "When I was on
board the Beagle I believed in the permanence of species, but as far as I can
remember vague doubts occasionally flitted across my mind." Unless
Prof. Judd and I are altogether wrong in believing that late or early
in the voyage (it matters little which) a definite approach was made
to the evolutionary standpoint, we must suppose that in 40 years such
advance had shrunk in his recollection to the dimensions of "vague
doubts." The letter to Zacharias shows I think some forgetting of the
past where the author says, "But I did not become convinced that
species were mutable until, I think, two or three years had elapsed."
It is impossible to reconcile this with the contents of the
evolutionary Note Book of 1837. I have no doubt that in his retrospect
he felt that he had not been "convinced that species were mutable" until he had gained a clear conception of the mechanism of natural
selection, i.e. in 1838-9.

But even on this last date there is some room, not for
doubt, but
for surprise. The passage in the Autobiography2 is quite
clear, namely that in October 1838 he read Malthus's Essay on the
principle of Population and "being well prepared to appreciate
the struggle for existence..., it at once struck me that under these
circumstances favourable variations would tend to be preserved,

and unfavourable ones to be destroyed. The result of this
would be
the formation of new species. Here then I had at last got a theory by
which to work."

It is surprising that Malthus should have been needed to
give him
the clue, when in the Note Book of 1837 there should occur—however
obscurely expressed—the following forecast1 of the
importance of the survival of the fittest. "With respect to extinction,
we can easily see that a variety of the ostrich (Petise2),
may not be well adapted, and thus perish out; or on the other hand,
like Orpheus3, being favourable, many might be produced.
This requires the principle that the permanent variations produced by
confined breeding and changing circumstances are continued and
produce<d> according to the adaptation of such circumstances, and
therefore that death of species is a consequence (contrary to what
would appear in America) of non-adaptation of circumstances."

I can hardly doubt, that with his knowledge of the
interdependence
of organisms and the tyranny of conditions, his experience would have
crystallized out into "a theory by which to work" even without the aid
of Malthus.

In my father's Autobiography4 he writes, "In
June 1842 I
first allowed myself the satisfaction of writing a very brief abstract
of my theory in pencil in 35 pages; and this was enlarged during the
summer of 1844 into one of 230 pages5, which I had fairly
copied out and still possess." These two Essays, of 1842 and 1844, are
now printed under the title The Foundations of the Origin of
Species.

1Life and Letters, ii.
p. 8.

2 Avestruz Petise, i.e.
Rhea Darwini.

3A bird.

4Life and Letters, i.
p. 84.

5 It contains as a fact 231 pp.
It is a
strongly bound folio, interleaved with blank pages, as though for notes
and additions. His own MS. from which it was
copied
contains 189 pp.

It will be noted that in the above passage he does not
mention the MS.
of 1842 as being in existence, and when I was at work on Life
and Letters I had not seen it. It only came to light after my
mother's death in 1896 when the house at Down was vacated. The MS.
was
hidden in a cupboard under the stairs which was not used for papers of
any value, but rather as an overflow for matter which he did not wish
to destroy.

The statement in the Autobiography that the MS.
was
written in 1842
agrees with an entry in my father's Diary:—

"1842. May 18th went to Maer. June 15th to Shrewsbury, and
on 18th
to Capel Curig....During my stay at Maer and Shrewsbury (five years
after commencement) wrote pencil sketch of my species theory." Again in
a letter to Lyell (June 18, 1858) he speaks of his "MS.
sketch written
out in 18421." In the Origin of Species, Ed. i. p.
1, he speaks of beginning his speculations in 1837 and of allowing
himself to draw up some "short notes" after "five years' work," i.e. in 1842. So far there seems no doubt as to 1842 being the date of
the first sketch; but there is evidence in favour of an earlier date2.
Thus across the Table of Contents of the bound copy of the 1844 MS.
is
written in my father's hand "This was sketched in 1839." Again in a
letter to Mr Wallace3 (Jan. 25, 1859) he speaks of his own
contributions to the Linnean paper4 of July 1, 1858, as
"written in 1839, now just twenty years ago." This statement as it
stands is undoubtedly incorrect, since the extracts are from the MS.
of
1844, about the date of which no doubt exists; but even if it could be
supposed to refer to the 1842 Essay, it must, I think, be rejected. I
can only account for his mistake by the supposition that my father had
in

mind the date (1839) at which the framework of his theory
was laid
down. It is worth noting that in his Autobiography (p. 88) he speaks of
the time "about 1839, when the theory was clearly conceived." However
this may be there can be no doubt that 1842 is the correct date. Since
the publication of Life and Letters I have gained fresh
evidence on this head. A small packet containing 13 pp. of MS.
came to
light in 1896. On the outside is written "First Pencil Sketch of
Species Theory. Written at Maer and Shrewsbury during May and June
1842." It is not however written in pencil, and it consists of a single
chapter on The Principles of Variation in Domestic Organisms. A
single unnumbered page is written in pencil, and is headed "Maer, May
1842, useless"; it also bears the words "This page was thought of as
introduction." It consists of the briefest sketch of the geological
evidence for evolution, together with words intended as headings for
discussion,—such as "Affinity,—unity of type,—fœtal state,—abortive
organs."

The back of this "useless" page is of some interest,
although it
does not bear on the question of date,—the matter immediately before us.

It seems to be an outline of the Essay or sketch of 1842,
consisting
of the titles of the three chapters of which it was to have consisted.

"I. The Principles of Var. in domestic organisms.

"II. The possible and probable application of
these same
principles to wild animals and consequently the possible and probable
production of wild races, analogous to the domestic ones of plants and
animals.

"III. The reasons for and against believing that such
races have
really been produced, forming what are called species."

designed corresponds to Part II (p. 22) of the Essay of
1842, which
is (p. 7) defined by the author as discussing "whether the characters
and relations of animated things are such as favour the idea of wild
species being races descended from a common stock." Again at p. 23 the
author asks "What then is the evidence in favour of it <the theory of
descent> and what the evidence against it." The generalised section of
his Essay having been originally Chapter III1 accounts for
the curious error which occurs in pp. 18 and 22 where the second Part
of the Essay is called Part III.

The division of the Essay into two parts is maintained in
the
enlarged Essay of 1844, in which he writes: "The Second Part of this
work is devoted to the general consideration of how far the general
economy of nature justifies or opposes the belief that related species
and genera are descended from common stocks." The Origin of
Species however is not so divided.

We may now return to the question of the date of the
Essay. I have
found additional evidence in favour of 1842 in a sentence written on
the back of the Table of Contents of the 1844 MS.—not
the copied
version but the original in my father's writing: "This was written and
enlarged from a sketch in 37 pages2 in Pencil (the latter
written in summer of 1842 at Maer and Shrewsbury) in beginning of 1844,
and finished it <sic>
in July; and finally corrected the
copy by Mr Fletcher in the last week in September." On the whole it is
impossible to doubt that 1842 is the date of the earlier of the two
Essays.

1 It is evident that Parts and Chapters were to some extent interchangeable in the author's mind, for p. 1
(of the MS. we have been discussing) is
headed in ink
Chapter I, and
afterwards altered in pencil to Part I.

2 On p. 23 of the MS.
of
the Foundations is a reference to the "back of p. 21 bis": this suggests that
additional pages had been interpolated in the MS.
and
that it may once
have had 37 in place of 35 pp.

The sketch of 1842 is written on bad paper with a soft
pencil, and
is in many parts extremely difficult to read, many of the words ending
in mere scrawls and being illegible without context. It is evidently
written rapidly, and is in his most elliptical style, the articles
being frequently omitted, and the sentences being loosely composed and
often illogical in structure. There is much erasure and correction,
apparently made at the moment of writing, and the MS.
does not give the
impression of having been re-read with any care. The whole is more like
hasty memoranda of what was clear to himself, than material for the
convincing of others.

Many of the pages are covered with writing on the back, an
instance
of his parsimony in the matter of paper1. This matter
consists partly of passages marked for insertion in the text, and these
can generally (though by no means always) be placed where he intended.
But he also used the back of one page for a preliminary sketch to be
rewritten on a clean sheet. These parts of the work have been printed
as footnotes, so as to allow what was written on the front of the pages
to form a continuous text. A certain amount of repetition is
unavoidable, but much of what is written on the backs of the pages is
of too much interest to be omitted. Some of the matter here given in
footnotes may, moreover, have been intended as the final text and not
as the preliminary sketch.

When a word cannot be deciphered, it is replaced
by:—<illegible>,
the
angular brackets being, as already explained, a symbol for an insertion
by the editor. More commonly, however, the context makes the
interpretation of a word reasonably sure although the word is not
strictly legible. Such words are followed by an inserted mark of
interrogation <?>.

Lastly, words inserted by the editor, of which the
appropriateness
is doubtful, are printed thus <variation?>.

Two kinds of erasure occur in the MS.
of 1842. One
by vertical lines
which seem to have been made when the 35 pp. MS.
was
being expanded
into that of 1844, and merely imply that such a page is done with: and
secondly the ordinary erasures by horizontal lines. I have not been
quite consistent in regard to these: I began with the intention of
printing (in square brackets) all such erasures. But I ultimately found
that the confusion introduced into the already obscure sentences was
greater than any possible gain; and many such erasures are altogether
omitted. In the same way I have occasionally omitted hopelessly obscure
and incomprehensible fragments, which if printed would only have
burthened the text with a string of <illegible>s and queried
words. Nor
have I printed the whole of what is written on the backs of the pages,
where it seemed to me that nothing but unnecessary repetition would
have been the result.

In the matter of punctuation I have given myself a free
hand. I may
no doubt have misinterpreted the author's meaning in so doing, but
without such punctuation, the number of repellantly crabbed sentences
would have been even greater than at present. In dealing with the Essay
of 1844, I have corrected some obvious slips without indicating such
alterations, because the MS. being legible,
there is no
danger of
changing the author's meaning.

The sections into which the Essay of 1842 is divided are
in the
original merely indicated by a gap in the MS.
or by a
line drawn across
the page. No titles are given except in the case of § VIII.;
and § II. is
the only section which has a number in the original. I might equally
well have made sections of what are now subsections, e.g. Natural

Selection p. 7, or Extermination p.
28. But
since the present sketch is the germ of the Essay of 1844, it seemed
best to preserve the identity between the two works, by using such of
the author's divisions as correspond to the chapters of the enlarged
version of 1844. The geological discussion with which Part II begins
corresponds to two chapters (IV and V) of the 1844 Essay. I have
therefore described it as §§ IV. and V.,
although I cannot make sure of
its having originally consisted of two sections. With this exception
the ten sections of the Essay of 1842 correspond to the ten chapters of
that of 1844.

The Origin of Species differs from the sketch
of 1842 in
not being divided into two parts. But the two volumes resemble each
other in general structure. Both begin with a statement of what may be
called the mechanism of evolution,—variation and selection: in both the
argument proceeds from the study of domestic organisms to that of
animals and plants in a state of nature. This is followed in both by a
discussion of the Difficulties on Theory and this by a
section Instinct which in both cases is treated as a special
case of difficulty.

If I had to divide the Origin (first edition)
into two
parts without any knowledge of earlier MS.,
I should, I
think, make
Part II begin with Ch. VI, Difficulties on Theory. A
possible reason why this part of the argument is given in Part I of the
Essay of 1842 may be found in the Essay of 1844, where it is clear that
the chapter on instinct is placed in Part I because the author thought
it of importance to show that heredity and variation occur in mental
attributes. The whole question is perhaps an instance of the sort of
difficulty which made the author give up the division of his argument
into two Parts when he wrote the Origin. As matters stand
§§ IV. and V. of
the 1842 Essay
correspond to

the geological chapters, IX and X, in the Origin. From
this point onwards the material is grouped in the same order in both
works: geographical distribution; affinities and classification; unity
of type and morphology; abortive or rudimentary organs; recapitulation
and conclusion.

In enlarging the Essay of 1842 into that of 1844, the
author
retained the sections of the sketch as chapters in the completer
presentment. It follows that what has been said of the relation of the
earlier Essay to the Origin is generally true of the 1844
Essay. In the latter, however, the geological discussion is, clearly
instead of obscurely, divided into two chapters, which correspond
roughly with Chapters IX and X of the Origin. But part of
the contents of Chapter X (Origin) occurs in Chapter VI
(1844) on Geographical Distribution. The treatment of distribution is
particularly full and interesting in the 1844 Essay, but the
arrangement of the material, especially the introduction of § III.
p.
183, leads to some repetition which is avoided in the Origin. It
should be noted that Hybridism, which has a separate chapter (VIII) in
the Origin, is treated in Chapter II of the Essay. Finally
that Chapter XIII (Origin) corresponds to Chapters VII, VIII
and IX of the work of 1844.

The fact that in 1842, seventeen years before the
publication of the Origin, my father should have been able to write out so full
an outline of his future work, is very remarkable. In his Autobiography1 he writes of the 1844 Essay, "But at that time I overlooked one
problem of great importance....This problem is the tendency in organic
beings descended from the same stock to diverge in character as they
become modified." The absence of the principle of divergence is of
course also a characteristic of the

sketch of 1842. But at p. 37, the author is not far from
this point
of view. The passage referred to is: "If any species, A, in
changing gets an advantage and that advantage...is inherited, A will
be the progenitor of several genera or even families in the hard
struggle of nature. A will go on beating out other forms, it
might come that A would people <the> earth,—we may now
not
have one descendant on our globe of the one or several original
creations1." But if the descendants of A have
peopled the earth by beating out other forms, they must have diverged
in occupying the innumerable diverse modes of life from which they
expelled their predecessors. What I wrote2 on this subject
in 1887 is I think true: "Descent with modification implies divergence,
and we become so habituated to a belief in descent, and therefore in
divergence, that we do not notice the absence of proof that divergence
is in itself an advantage."

The fact that there is no set discussion on the principle
of
divergence in the 1844 Essay, makes it clear why the joint paper read
before the Linnean Society on July 1, 1858, included a letter3 to Asa Gray, as well as an extract4 from the Essay of 1844.
It is clearly because the letter to Gray includes a discussion on
divergence, and was thus, probably, the only document, including this
subject, which could be appropriately made use of. It shows once more
how great was the importance attached by its author to the principle of
divergence.

I have spoken of the hurried and condensed manner in which
the
sketch of 1842 is written; the style of the later Essay (1844) is more
finished.

1 In the footnotes to the Essay
of 1844
attention is called to similar passages.

2Life and Letters,
ii. p. 15.

3 The passage is given in the Life
and Letters, ii. p. 124.

4 The extract consists of the
section on Natural
Means of Selection, p. 87.

It has, however, the air of an uncorrected MS.
rather than of a book
which has gone through the ordeal of proof sheets. It has not all the
force and conciseness of the Origin, but it has a certain
freshness which gives it a character of its own. It must be remembered
that the Origin was an abstract or condensation of a much
bigger book, whereas the Essay of 1844 was an expansion of the sketch
of 1842. It is not therefore surprising that in the Origin there
is occasionally evident a chafing against the author's self-imposed
limitation. Whereas in the 1844 Essay there is an air of freedom, as if
the author were letting himself go, rather than applying the curb. This
quality of freshness and the fact that some questions were more fully
discussed in 1844 than in 1859, makes the earlier work good reading
even to those who are familiar with the Origin.

The writing of this Essay "during the summer of 1844," as
stated in
the Autobiography1, and "from memory," as Darwin says
elsewhere2, was a remarkable achievement, and possibly
renders more conceivable the still greater feat of the writing of the Origin between July 1858 and September 1859.

It is an interesting subject for speculation: what
influence on the
world the Essay of 1844 would have exercised, had it been published in
place of the Origin. The author evidently thought of its
publication in its present state as an undesirable expedient, as
appears clearly from the following extracts from the Life and
Letters, vol. ii. pp. 16-18:

"...I have just finished my sketch of my species theory.
If, as I
believe, my theory in time be accepted even by one competent judge, it
will be a considerable step in science.

"I therefore write this in case of my sudden death, as my
most
solemn and last request, which I am sure you will consider the same as
if legally entered in my will, that you will devote £400 to its
publication, and further will yourself, or through Hensleigh1,
take trouble in promoting it. I wish that my sketch be given to some
competent person, with this sum to induce him to take trouble in its
improvement and enlargement. I give to him all my books on Natural
History, which are either scored or have references at the end to the
pages, begging him carefully to look over and consider such passages as
actually bearing, or by possibility bearing, on this subject. I wish
you to make a list of all such books as some temptation to an editor. I
also request that you will hand over <to> him all those scraps
roughly
divided into eight or ten brown paper portfolios. The scraps, with
copied quotations from various works, are those which may aid my
editor. I also request that you, or some amanuensis, will aid in
deciphering any of the scraps which the editor may think possibly of
use. I leave to the editor's judgment whether to interpolate these
facts in the text, or as notes, or under appendices. As the looking
over the references and scraps will be a long labour, and as the correcting and enlarging and altering my sketch will also take considerable
time, I leave this sum of £400 as some remuneration, and any profits
from

the work. I consider that for this the editor is bound to
get the
sketch published either at a publisher's or his own risk. Many of the
scraps in the portfolios contain mere rude suggestions and early views,
now useless, and many of the facts will probably turn out as having no
bearing on my theory.

"With respect to editors, Mr Lyell would be the best if he
would
undertake it; I believe he would find the work pleasant, and he would
learn some facts new to him. As the editor must be a geologist as well
as a naturalist, the next best editor would be Professor Forbes of
London. The next best (and quite best in many respects) would be
Professor Henslow. Dr Hooker would be very good. The next,
Mr Strickland1. If none of these would undertake it, I would
request you to consult with Mr Lyell, or some other capable man, for
some editor, a geologist and naturalist. Should one other hundred
pounds make the difference of procuring a good editor, I request
earnestly that you will raise £500.

"My remaining collections in Natural History may be given
to any one
or any museum where <they> would be accepted...."

<The following note seems to have formed part of the
original
letter, but may have been of later date:>

"Lyell, especially with the aid of Hooker (and of any good
zoological aid), would be best of all. Without an editor will pledge
himself to give up time to it, it would be of no use paying such a sum.

"If there should be any difficulty in getting an editor
who would go
thoroughly into the subject,

1 After Mr Strickland's name
comes the
following sentence, which has been erased, but remains legible.
"Professor Owen would be very good; but I presume he would not
undertake such a work."

and think of the bearing of the passages marked in the
books and
copied out of scraps of paper, then let my sketch be published as it
is, stating that it was done several years ago1, and from
memory without consulting any works, and with no intention of
publication in its present form."

The idea that the sketch of 1844 might remain, in the
event of his
death, as the only record of his work, seems to have been long in his
mind, for in August, 1854, when he had finished with the Cirripedes,
and was thinking of beginning his "species work," he added on the back
of the above letter, "Hooker by far best man to edit my species volume.
August 1854."

I have called attention in footnotes to many points in
which the Origin agrees with the Foundations. One of the most
interesting is the final sentence, practically the same in the Essays
of 1842 and 1844, and almost identical with the concluding words of the Origin. I have elsewhere pointed out2 that the
ancestry of this eloquent passage may be traced one stage further
back,—to the Note Book of 1837. I have given this sentence as an
appropriate motto for the Foundations in its character of a
study of general laws. It will be remembered that a corresponding motto
from Whewell's Bridgewater Treatise is printed opposite the
title-page of the Origin of Species.

Mr Huxley who, about the year 1887, read the Essay of
1844, remarked
that "much more weight is attached to the influence of external
conditions in producing variation and to the inheritance of acquired
habits than in the Origin."In the Foundations the effect of conditions is frequently mentioned, and Darwin seems
to have had constantly

1 The words "several years ago,
and" seem
to have been added at a later date.

in mind the need of referring each variation to a cause.
But I gain
the impression that the slighter prominence given to this view in the Origin was not due to change of opinion, but rather because he had
gradually come to take this view for granted; so that in the scheme of
that book, it was overshadowed by considerations which then seemed to
him more pressing. With regard to the inheritance of acquired
characters I am not inclined to agree with Huxley. It is certain that
the Foundations contains strong recognition of the
importance of germinal variation, that is of external conditions acting
indirectly through the "reproductive functions." He evidently
considered this as more important than the inheritance of habit or
other acquired peculiarities.

Another point of interest is the weight he attached in
1842-4 to
"sports" or what are now called "mutations." This is I think more
prominent in the Foundations than in the first edition of
the Origin, and certainly than in the fifth and sixth
editions.

Among other interesting points may be mentioned the "good
effects of
crossing" being "possibly analogous to good effects of change in
condition,"—a principle which he upheld on experimental grounds in his Cross and Self-Fertilisation in 1876.

In conclusion, I desire to express my thanks to Mr Wallace
for a
footnote he was good enough to supply: and to Professor Bateson, Sir W.
Thiselton-Dyer, Dr Gadow, Professor Judd, Dr Marr, Col. Prain and Dr
Stapf for information on various points. I am also indebted to Mr
Rutherford, of the University Library, for his careful copy of the
manuscript of 1842.

§ I. <ON VARIATION UNDER
DOMESTICATION, AND ON THE
PRINCIPLES OF SELECTION.>

AN individual organism placed under new conditions [often]
sometimes
varies in a small degree and in very trifling respects such as stature,
fatness, sometimes colour, health, habits in animals and probably
disposition. Also habits of life develope certain parts. Disuse
atrophies. [Most of these slight variations tend to become hereditary.]

When the individual is multiplied for long periods by buds
the
variation is yet small, though greater and occasionally a single bud or
individual departs widely from its type (example)1 and
continues steadily to propagate, by buds, such new kind.

When the organism is bred for several generations under
new or
varying conditions, the variation is greater in amount and endless in
kind [especially2 holds good when individuals have long
been exposed to new conditions]. The nature of the external conditions
tends to effect some definite change in all or greater part of
offspring,—little food, small size—certain foods harmless &c.
&c. organs affected and diseases—extent unknown. A certain degree of

1 Evidently a memorandum that an
example
should be given.

2 The importance of exposure to
new
conditions for several generations is insisted on in the Origin,
Ed. i. p. 7, also p. 131. In the latter passage the author guards
himself against the assumption that variations are "due to chance," and
speaks of "our ignorance of the cause of each particular variation."
These statements are not always remembered by his critics.

variation (Müller's twins)1 seems inevitable
effect of
process of reproduction. But more important is that simple <?>
generation, especially under new conditions [when no crossing] <causes>
infinite variation and not direct effect of external conditions, but
only in as much as it affects the reproductive functions2.
There seems to be no part (beau ideal of liver)3 of body, internal or external, or mind or habits, or instincts which
does not vary in some small degree and [often] some <?> to a
great
amount.

[All such] variations [being congenital] or those very
slowly
acquired of all kinds [decidedly evince a tendency to become
hereditary], when not so become simple variety, when it does a race.
Each4 parent transmits its peculiarities, therefore if
varieties allowed freely to cross, except by the chance of
two characterized by same peculiarity happening to marry, such
varieties will be constantly demolished5. All bisexual
animals must cross, hermaphrodite plants do cross, it seems very
possible that her-

1 Cf. Origin, Ed. i.
p. 10, vi.
p. 9, "Young of the same litter, sometimes differ considerably from
each other, though both the young and the parents, as Müller has
remarked, have apparently been exposed to exactly the same conditions
of life."

2 This is paralleled by the
conclusion in
the Origin, Ed. i. p. 8, that "the most frequent cause of
variability may be attributed to the male and female reproductive
elements having been affected prior to the act of conception."

3 The meaning seems to be that
there must
be some variability in the liver otherwise anatomists would not speak
of the 'beau ideal' of that organ.

4 The position of the following
passage is
uncertain. "If individuals of two widely different varieties be allowed
to cross, a third race will be formed—a most fertile source of the
variation in domesticated animals. <In the Origin, Ed. i.
p.
20 the author says that "the possibility of making distinct races by
crossing has been greatly exaggerated."> If freely allowed, the
characters of pure parents will be lost, number of races thus
<illegible> but differences <?> besides the <illegible>. But if
varieties differing in very slight respects be allowed to cross, such
small variation will be destroyed, at least to our senses,—a variation
[clearly] just to be distinguished by long legs will have offspring not
to be so distinguished. Free crossing great agent in producing
uniformity in any breed. Introduce tendency to revert to parent form."

5 The swamping effect of
intercrossing is
referred to in the Origin, Ed. i. p. 103, vi. p. 126.

maphrodite animals do cross,—conclusion strengthened: ill
effects of
breeding in and in, good effects of crossing possibly analogous to good
effects of change in condition <?>1.

Therefore if in any country or district all animals of one
species
be allowed freely to cross, any small tendency in them to vary will be
constantly counteracted. Secondly reversion to parent form—analogue of vis
medicatrix2. But if man selects, then new
races rapidly formed,—of late years systematically followed,—in most
ancient times often practically followed3. By such selection
make race-horse, dray-horse—one cow good for tallow, another for eating
&c.—one plant's good lay <illegible> in leaves another in
fruit
&c. &c.: the same plant to supply his wants at different times
of year. By former means animals become adapted, as a direct effect to
a cause, to external conditions, as size of body to amount of food. By
this latter means they may also be so adapted, but further they may be
adapted to ends and pursuits, which by no possibility can affect
growth, as existence of tallow-chandler cannot tend to make fat. In
such selected races, if not removed to new conditions, and <if>
preserved from all cross, after several generations become very true,
like each other and not varying. But man4 selects only <?>
what is useful and curious—has bad judgment, is capricious,—grudges to
destroy those that do not come up to his pattern,—has no

1 A discussion on the
intercrossing of
hermaphrodites in relation to Knight's views occurs in the Origin, Ed. i. p. 96, vi. p. 119. The parallelism between crossing and
changed conditions is briefly given in the Origin, Ed. i. p.
267, vi. p. 391, and was finally investigated in The Effects of
Cross and Self-Fertilisation in the Vegetable Kingdom, 1876.

2 There is an article on the vis
medicatrix in Brougham's Dissertations,1839,
a copy of which is in the author's library.

3 This is the classification of
selection
into methodical and unconscious given in the Origin, Ed. i.
p. 33, vi. p. 38.

4 This passage, and a similar
discussion
on the power of the Creator (p. 6), correspond to the comparison
between the selective capacities of man and nature, in the Origin,
Ed. i. p. 83, vi. p. 102.

[knowledge] power of selecting according to internal
variations,—can
hardly keep his conditions uniform,—[cannot] does not select those best
adapted to the conditions under which <the> form <?> lives,
but those
most useful to him. This might all be otherwise.

§ II. <ON VARIATION IN A STATE
OF
NATURE AND ON THE
NATURAL MEANS OF SELECTION.>

Let us see how far above principles of variation apply to
wild
animals. Wild animals vary exceedingly little—yet they are known as
individuals1. British Plants, in many genera number quite
uncertain of varieties and species: in shells chiefly external
conditions2. Primrose and cowslip. Wild animals from
different [countries can be recognized]. Specific character gives some
organs as varying. Variations analogous in kind, but less in degree
with domesticated animals—chiefly external and less important parts.

Our experience would lead us to expect that any and every
one of
these organisms would vary if <the organism were> taken away <?>
and
placed under new conditions. Geology proclaims a constant round of
change, bringing into play, by every possible <?> change of
climate and
the death of pre-existing inhabitants, endless variations of new
conditions. These <?> generally very slow, doubtful though <illegible>
how far the slowness <?> would produce tendency to vary. But
Geolog<ists> show change in configuration which, together with the
accidents of air and water and the means of transportal which every
being possesses, must occasionally bring, rather suddenly, organism to
new conditions and <?> expose it for several generations.

Hence <?> we should expect every now and then a wild
form
to vary1;
possibly this may be cause of some species varying more than others.

According to nature of new conditions, so we might expect
all or
majority of organisms born under them to vary in some definite way.
Further we might expect that the mould in which they are cast would
likewise vary in some small degree. But is there any means of selecting
those offspring which vary in the same manner, crossing them and
keeping their offspring separate and thus producing selected races:
otherwise as the wild animals freely cross, so must such small
heterogeneous varieties be constantly counter-balanced and lost, and a
uniformity of character [kept up] preserved. The former variation as
the direct and necessary effects of causes, which we can see can act on
them, as size of body from amount of food, effect of certain kinds of
food on certain parts of bodies &c. &c.; such new varieties may
then become adapted to those external [natural] agencies which act on
them. But can varieties be produced adapted to end, which cannot
possibly influence their structure and which it is absurd to look <at>
as effects of chance. Can varieties like some vars of domesticated
animals, like almost all wild species be produced adapted by exquisite
means to prey on one animal or to escape from another,—or rather, as it
puts out of question effects of intelligence and habits, can a plant
become adapted to animals, as a plant which cannot be impregnated
without agency of insect; or hooked seeds depending on animal's
existence: woolly animals cannot have any direct effect on seeds of
plant. This point which all theories about

1 When the author wrote this
sketch he
seems not to have been so fully convinced of the general occurrence of
variation in nature as he afterwards became. The above passage in the
text possibly suggests that at this time he laid more stress on sports or mutations than was afterwards the case.

climate adapting woodpecker1to crawl
<?> up
trees, <illegible> miseltoe, <sentence incomplete>. But if every
part
of a plant or animal was to vary <illegible>, and if a being
infinitely
more sagacious than man (not an omniscient creator) during thousands
and thousands of years were to select all the variations which tended
towards certain ends ([or were to produce causes <?> which tended
to
the same end]), for instance, if he foresaw a canine animal would be
better off, owing to the country producing more hares, if he were
longer legged and keener sight,—greyhound produced2. If he
saw that aquatic (animal would need) skinned toes. If for some unknown
cause he found it would advantage a plant, which <?> like most
plants
is occasionally visited by bees &c.: if that plant's seed were
occasionally eaten by birds and were then carried on to rotten trees,
he might select trees with fruit more agreeable to such birds as
perched, to ensure their being carried to trees; if he perceived those
birds more often dropped the seeds, he might well have selected a bird
who would <illegible> rotten trees or [gradually select plants
which <he> had proved to live on less and less rotten trees]. Who,
seeing how
plants vary in garden, what blind foolish man has done3 in a
few years, will deny an all-seeing being in thousands of years could
effect (if the Creator chose to do so), either by his own direct
foresight or by intermediate means,—which will represent <?> the
creator of this universe. Seems usual means. Be it remembered I have
nothing to say about life and mind and all

1 The author may possibly have
taken the
case of the woodpecker from Buffon, Histoire Nat. des Oiseaux,
T. vii. p. 3, 1780, where however it is treated from a different point
of view. He uses it more than once, see for instance Origin,
Ed. i. pp. 3, 60, 184, vi. pp. 3, 76, 220. The passage in the text
corresponds with a discussion on the woodpecker and the mistletoe in Origin,
Ed. i. p. 3, vi. p. 3.

forms descending from one common type1. I speak
of the
variation of the existing great divisions of the organised kingdom, how
far I would go, hereafter to be seen.

Before considering whether <there> be any natural means of
selection, and secondly (which forms the 2nd Part of this sketch) the
far more important point whether the characters and relations of
animated <things> are such as favour the idea of wild species being
races <?> descended from a common stock, as the varieties of
potato or
dahlia or cattle having so descended, let us consider probable
character of [selected races] wild varieties.

Natural Selection. De Candolle's war of
nature,—seeing
contented face of nature,—may be well at first doubted; we see it on
borders of perpetual cold2. But considering the enormous
geometrical power of increase in every organism and as <?> every
country, in ordinary cases <countries> must be stocked to full extent,
reflection will show that this is the case. Malthus on man,—in animals
no moral [check] restraint <?>—they breed in time of year when
provision most abundant, or season most favourable, every country has
its seasons,—calculate robins,—oscillating from years of destruction3.
If proof were wanted let any singular change of climate <occur> here
<?>, how astoundingly some tribes <?> increase, also
introduced animals4,
the

1 Note in the original. "Good
place to
introduce, saying reasons hereafter to be given, how far I extend
theory, say to all mammalia—reasons growing weaker and weaker."

2 See Origin, Ed. i.
pp. 62, 63,
vi. p. 77, where similar reference is made to De Candolle; for Malthus
see Origin, p. 5.

3 This may possibly refer to the
amount of
destruction going on. See Origin, Ed. i. p. 68, vi. p. 84,
where there is an estimate of a later date as to death-rate of birds in
winter. "Calculate robins" probably refers to a calculation of the rate
of increase of birds under favourable conditions.

4 In the Origin, Ed.
i. pp. 64,
65, vi. p. 80, he instances cattle and horses and certain plants in S.
America and American species of plants in India, and further on, as
unexpected effects of changed conditions, the enclosure of a heath, and
the relation between the fertilisation of clover and the presence of
cats (Origin, Ed. i. p. 74, vi. p. 91).

pressure is always ready,—capacity of alpine plants to
endure other
climates,—think of endless seeds scattered abroad,—forests regaining
their percentage1,—a thousand wedges2 are being
forced into the œconomy of nature. This requires much reflection; study
Malthus and calculate rates of increase and remember the
resistance,—only periodical.

The unavoidable effect of this <is> that many of every
species are
destroyed either in egg or [young or mature (the former state the more
common)]. In the course of a thousand generations infinitesimally small
differences must inevitably tell3; when unusually cold
winter, or hot or dry summer comes, then out of the whole body of
individuals of any species, if there be the smallest differences in
their structure, habits, instincts [senses], health &c., <it> will
on an average tell; as conditions change a rather larger proportion
will be preserved: so if the chief check to increase falls on seeds or
eggs, so will, in the course of 1000 generations or ten thousand, those
seeds (like one with down to fly4) which fly furthest and
get scattered most ultimately rear most plants, and such small
differences tend to be hereditary like shades of expression in human
countenance. So if one parent <?> fish deposits its egg in
infinitesimally different circumstances, as in rather shallower or
deeper water &c., it will then <?> tell.

Let hares5 increase very slowly from change of
climate
affecting peculiar plants, and some other <illegible> rabbit
decrease
in same proportion [let this unsettle organisation of], a canine
animal, who

1Origin, Ed. i. p.
74, vi. p.
91. "It has been observed that the trees now growing on...ancient
Indian mounds...display the same beautiful diversity and proportion of
kinds as in the surrounding virgin forests."

2 The simile of the wedge occurs
in the Origin, Ed. i. p. 67; it is deleted in Darwin's copy of the first edition:
it does not occur in Ed. vi.

3In a rough summary
at the
close of the Essay, occur the words:— "Every creature lives by a
struggle, smallest grain in balance must tell."

formerly derived its chief sustenance by springing on
rabbits or
running them by scent, must decrease too and might thus readily become
exterminated. But if its form varied very slightly, the long legged
fleet ones, during a thousand years being selected, and the less fleet
rigidly destroyed must, if no law of nature be opposed to it, alter
forms.

Remember how soon Bakewell on the same principle altered
cattle and
Western, sheep,—carefully avoiding a cross (pigeons) with any breed. We
cannot suppose that one plant tends to vary in fruit and another in
flower, and another in flower and foliage,—some have been selected for
both fruit and flower: that one animal varies in its covering and
another not,—another in its milk. Take any organism and ask what is it
useful for and on that point it will be found to vary,—cabbages in
their leaf,—corn in size <and> quality of grain, both in times of
year,—kidney beans for young pod and cotton for envelope of seeds
&c. &c.: dogs in intellect, courage, fleetness and smell <?>:
pigeons in peculiarities approaching to monsters. This requires
consideration,—should be introduced in first chapter if it holds, I
believe it does. It is hypothetical at best1.

Nature's variation far less, but such selection far more
rigid and
scrutinising. Man's races not [even so well] only not better adapted to
conditions than other races, but often not <?> one race adapted
to its
conditions, as man keeps and propagates some alpine plants in garden.
Nature lets <an> animal live, till on actual proof it is found less
able to do the required work to serve the desired end, man judges
solely by his eye, and knows not whether

1 Compare Origin, Ed.
i. p. 41,
vi. p. 47. "I have seen it gravely remarked, that it was most fortunate
that the strawberry began to vary just when gardeners began to attend
closely to this plant. No doubt the strawberry had always varied since
it was cultivated, but the slight varieties had been neglected."

nerves, muscles, arteries, are developed in proportion to
the change
of external form.

Besides selection by death, in bisexual animals
<illegible> the
selection in time of fullest vigour, namely struggle of males; even in
animals which pair there seems a surplus <?> and a battle,
possibly as
in man more males produced than females, struggle of war or charms1.
Hence that male which at that time is in fullest vigour, or best armed
with arms or ornaments of its species, will gain in hundreds of
generations some small advantage and transmit such characters to its
offspring. So in female rearing its young, the most vigorous and
skilful and industrious, <whose> instincts <are> best developed, will
rear more young, probably possessing her good qualities, and a greater
number will thus <be> prepared for the struggle of nature. Compared to
man using a male alone of good breed. This latter section only of
limited application, applies to variation of [specific] sexual
characters. Introduce here contrast with Lamarck,—absurdity of habit,
or chance ?? or external conditions, making a woodpecker adapted to tree2.

Before considering difficulties of theory of selection let
us
consider character of the races produced, as now explained, by nature.
Conditions have varied slowly and the organisms best adapted in their
whole course of life to the changed conditions have always been
selected,—man selects small dog and afterwards gives it profusion of
food,—selects a long-backed and short-legged breed and gives it no
particular exercise to suit this function &c. &c. In ordinary
cases nature has not allowed her race to

2 It is not obvious why the
author objects
to "chance" or "external conditions making a woodpecker." He allows
that variation is ultimately referable to conditions and that the
nature of the connexion is unknown, i.e. that the result is fortuitous.
It is not clear in the original to how much of the passage the two ?
refer.

be contaminated with a cross of another race, and
agriculturists
know how difficult they find always to prevent this,—effect would be
trueness. This character and sterility when crossed, and generally a
greater amount of difference, are two main features, which distinguish
domestic races from species.

[Sterility not universal admitted by all1. Gladiolus,
Crinum, Calceolaria2must be species if
there be such a thing. Races of dogs and oxen: but certainly very
general; indeed a gradation of sterility most perfect3 very
general. Some nearest species will not cross (crocus, some heath <?>),
some genera cross readily (fowls4 and grouse, peacock
&c.). Hybrids no ways monstrous quite perfect except secretions5 hence even the mule has bred,—character of sterility, especially
a few years ago <?> thought very much more universal than it now
is,
has been thought the distinguishing character; indeed it is obvious if
all forms freely crossed, nature would be a chaos. But the very
gradation of the character, even if it always existed in some degree
which it does not, renders it impossible as marks <?> those <?> suppose
distinct as species6]. Will analogy throw any light

1 The meaning is "That sterility
is not
universal is admitted by all."

2 See Var. under Dom.,
Ed. 2, i.
p. 388, where the garden forms of Gladiolus and Calceolaria are said to be derived from crosses between distinct species.
Herbert's hybrid Crinums are discussed in the Origin,
Ed. i. p. 250, vi. p. 370. It is well known that the author believed in
a multiple origin of domestic dogs.

3 The argument from gradation in
sterility
is given in the Origin, Ed. i. pp. 248, 255, vi. pp. 368,
375. In the Origin, I have not come across the cases
mentioned, viz. crocus, heath, or grouse and fowl or peacock. For
sterility between closely allied species, see Origin, Ed. i.
p. 257, vi. p. 377. In the present essay the author does not
distinguish between fertility between species and the fertility of the
hybrid offspring, a point on which he insists in the Origin, Ed.
i. p. 245, vi. p. 365.

4 Ackermann (Ber. d.
Vereins f.
Naturkunde zu Kassel, 1898, p. 23) quotes from Gloger that a cross
has been effected between a domestic hen and a Tetrao tetrix;
the offspring died when three days old.

5 No doubt the sexual cells are
meant. I
do not know on what evidence it is stated that the mule has bred.

6 The sentence is all but
illegible. I
think that the author refers to forms usually ranked as varieties
having been marked as species when it was

on the fact of the supposed races of nature being sterile,
though
none of the domestic ones are? Mr Herbert <and> Koelreuter have shown
external differences will not guide one in knowing whether hybrids will
be fertile or not, but the chief circumstance is constitutional
differences1, such as being adapted to different climate or
soil, differences which [must] probably affect the whole body of the
organism and not any one part. Now wild animals, taken out of their
natural conditions, seldom breed. I do not refer to shows or to
Zoological Societies where many animals unite, but <do not?> breed, and
others will never unite, but to wild animals caught and kept quite
tame left loose and well fed about houses and living many years.
Hybrids produced almost as readily as pure breds. St Hilaire great
distinction of tame and domestic,—elephants,—ferrets2.
Reproductive organs not subject to disease in Zoological Garden.
Dissection and microscope show that hybrid is in exactly same condition
as another animal in the intervals of breeding season, or those animals
which taken wild and not bred in domesticity, remain without
breeding their whole lives. It should be observed that so far from
domesticity being unfavourable in itself <it> makes more fertile: [when
animal is domesticated and breeds, productive power increased from more
food and selection of fertile races]. As far as animals go might be
thought <an> effect on their mind and a special case.

But turning to plants we find same class of facts. I do
not refer to
seeds not ripening, perhaps the com-

found that they were sterile together. See
the case
of the red and blue Anagallis given from Gärtner in the Origin,Ed. i. p. 247, vi. p. 368.

1 In the Origin, Ed.
i. p. 258,
where the author speaks of constitutional differences in this
connexion, he specifies that they are confined to the reproductive
system.

2 The sensitiveness of the
reproductive
system to changed conditions is insisted on in the Origin,
Ed. i. p. 8, vi. p. 10.

The ferret is mentioned, as being prolific
in
captivity, in Var. under Dom., Ed. 2, ii. p. 90.

monest cause, but to plants not setting, which either is
owing to
some imperfection of ovule or pollen. Lindley says sterility is the
[curse] bane of all propagators,—Linnæus about alpine plants. American
bog plants,—pollen in exactly same state as in hybrids,—same in
geraniums. Persian and Chinese1 lilac will not seed in
Italy and England. Probably double plants and all fruits owe their
developed parts primarily <?> to sterility and extra food thus <?>
applied2. There is here gradation <in> sterility and then
parts, like diseases, are transmitted hereditarily. We cannot assign
any cause why the Pontic Azalea produces plenty of pollen and not
American3, why common lilac seeds and not Persian, we see no
difference in healthiness. We know not on what circumstances these
facts depend, why ferret breeds, and cheetah4, elephant and
pig in India will not.

Now in crossing it is certain every peculiarity in form
and
constitution is transmitted: an alpine plant transmits its alpine
tendency to its offspring, an American plant its American-bog
constitution, and <with> animals, those peculiarities, on which5 when placed out of their natural conditions they are incapable of
breeding; and moreover they transmit every part of their constitution,
their

1 Lindley's remark is quoted in
the Origin,
Ed. i. p. 9. Linnæus' remark is to the effect that Alpine plants tend
to be sterile under cultivation (see Var. under Dom., Ed. 2,
ii. p. 147). In the same place the author speaks of peat-loving plants
being sterile in our gardens,—no doubt the American bog-plants referred
to above. On the following page (p. 148) the sterility of the lilac (Syringa
persica and chinensis) is referred to.

2 The author probably means that
the
increase in the petals is due to a greater food supply being available
for them owing to sterility. See the discussion in Var. under Dom.,
Ed. 2, ii. p. 151. It must be noted that doubleness of the flower may
exist without noticeable sterility.

3 I have not come across this
case in the
author's works.

4 For the somewhat doubtful case
of the
cheetah (Felis jubata) see Var. under Dom., Ed. 2,
ii. p. 133. I do not know to what fact "pig in India" refers.

5 This sentence should run "on
which
depends their incapacity to breed in unnatural conditions."

respiration, their pulse, their instinct, which are all
suddenly
modified, can it be wondered at that they are incapable of breeding? I
think it may be truly said it would be more wonderful if they did. But
it may be asked why have not the recognised varieties, supposed to have
been produced through the means of man, [not refused to breed] have all
bred1. Variation depends on change of condition and selection2,
as far as man's systematic or unsystematic selection <has> gone; he
takes external form, has little power from ignorance over internal
invisible constitutional differences. Races which have long been
domesticated, and have much varied, are precisely those which were
capable of bearing great changes, whose constitutions were adapted to a
diversity of climates. Nature changes slowly and by degrees. According
to many authors probably breeds of dogs are another case of modified
species freely crossing. There is no variety which <illegible>
has been <illegible> adapted to peculiar soil or situation for a
thousand years
and another rigorously adapted to another, till such can be produced,
the question is not tried3. Man in past ages, could
transport into different climates, animals and plants which would
freely propagate in such new climates. Nature could effect, with
selection, such changes slowly, so that precisely those animals which
are adapted to submit to great changes have given rise to diverse
races,—and indeed great doubt on this head4.

1 This sentence ends in
confusion: it
should clearly close with the words "refused to breed" in place of the
bracket and the present concluding phrase.

2 The author doubtless refers to
the
change produced by the summation of variation by means of
selection.

3 The meaning of this sentence
is made
clear by a passage in the MS. of
1844:—"Until man
selects two varieties
from the same stock, adapted to two climates or to other different
external conditions, and confines each rigidly for one or several
thousand years to such conditions, always selecting the individuals
best adapted to them, he cannot be said to have even commenced the
experiment." That is, the attempt to produce mutually sterile domestic
breeds.

4 This passage is to some extent
a
repetition of a previous one and may

Before leaving this subject well to observe that it was
shown that a
certain amount of variation is consequent on mere act of reproduction,
both by buds and sexually,—is vastly increased when parents exposed for
some generations to new conditions1, and we now find that
many animals when exposed for first time to very new conditions, are
<as> incapable of breeding as hybrids. It [probably] bears also on
supposed fact of crossed animals when not infertile, as in mongrels,
tending to vary much, as likewise seems to be the case, when true
hybrids possess just sufficient fertility to propagate with the parent
breeds and inter se for some generations. This is
Koelreuter's belief. These facts throw light on each other and support
the truth of each other, we see throughout a connection between the
reproductive faculties and exposure to changed conditions of life
whether by crossing or exposure of the individuals2.

Difficulties on theory of selection3. It
may be objected such perfect organs as eye and ear, could never be
formed, in latter less difficulty as gradations more perfect; at first
appears monstrous and to <the> end appears difficulty. But think of
gradation, even now manifest, (Tibia and Fibula). Everyone will allow
if every fossil preserved, gradation

have been intended to replace an earlier
sentence. I
have thought it best to give both. In the Origin, Ed. i. p.
141, vi. p. 176, the author gives his opinion that the power of
resisting diverse conditions, seen in man and his domestic animals, is
an example "of a very common flexibility of constitution."

1 In the Origin, Ed.
i. Chs. I.
and V., the author does not admit
reproduction, apart
from environment,
as being a cause of variation. With regard to the cumulative effect of
new conditions there are many passages in the Origin, Ed. i.
e.g. pp. 7, 12, vi. pp. 8, 14.

2 As already pointed out, this
is the
important principle investigated in the author's Cross and
Self-Fertilisation. Professor Bateson has suggested to me that
the experiments should be repeated with gametically pure individuals.

3 In the Origin a
chapter is
given up to "difficulties on theory": the discussion in the present
essay seems slight even when it is remembered how small a space is here
available. For Tibia &c. see p. 48.

infinitely more perfect; for possibility of selection
a perfect <?>
gradation is required. Different groups of structure, slight gradation
in each group,—every analogy renders it probable that intermediate
forms have existed. Be it remembered what strange metamorphoses; part
of eye, not directly connected with vision, might come to be [thus
used] gradually worked in for this end,—swimming bladder by gradation
of structure is admitted to belong to the ear
system,—rattlesnake.
[Woodpecker best adapted to climb.] In some cases
gradation not possible,—as vertebræ,—actually vary in domestic
animals,—less difficult if growth
followed. Looking to whole animals, a bat formed not for flight1.
Suppose we had flying fish2 and not one of our now called
flying fish preserved, who would have guessed intermediate habits.
Woodpeckers and tree-frogs both live in countries where no trees3.

The gradations by which each individual organ has arrived
at its
present state, and each individual animal with its aggregate of organs
has arrived, probably never could be known, and all present great
difficulties. I merely wish to show that the proposition is not so
monstrous as it at first appears, and that if good reason can be
advanced for believing the species have descended from common parents,
the difficulty of imagining intermediate forms of structure not
sufficient to make one at once reject the theory.

1 This may be interpreted "The
general
structure of a bat is the same as that of non-flying mammals."

2 That is truly winged fish.

3 The terrestrial woodpecker of
S. America
formed the subject of a paper by Darwin, Proc. Zool. Soc.,
1870. See Life and Letters, vol. iii. p. 153.

The mental powers of different animals in wild and tame
state
[present still greater difficulties] require a separate section. Be it
remembered I have nothing to do with origin of memory, attention, and
the different faculties of the mind1, but merely with their
differences in each of the great divisions of nature. Disposition,
courage, pertinacity <?>, suspicion, restlessness, ill-temper,
sagacity
and <the> reverse unquestionably vary in animals and are inherited
(Cuba wildness dogs, rabbits, fear against particular object as man
Galapagos2). Habits purely corporeal, breeding season
&c., time of going to rest &c., vary and are hereditary, like
the analogous habits of plants which vary and are inherited. Habits of
body, as manner of movement d°. and d°. Habits, as pointing and setting
on certain occasions d°. Taste for hunting certain objects and manner
of doing so,—sheep-dog. These are shown clearly by crossing and their
analogy with true instinct thus shown,—retriever. Do not know objects
for which they do it. Lord Brougham's definition3. Origin
partly habit, but the amount necessarily unknown, partly selection.
Young pointers pointing stones and sheep—tumbling pigeons—sheep4 going back to place where born.

1 The same proviso occurs in the Origin,
Ed. i. p. 207, vi. p. 319.

2The tameness of the
birds in
the Galapagos is described in the Journal of Researches (1860),
p. 398. Dogs and rabbits are probably mentioned as cases in which the
hereditary fear of man has been lost. In the 1844 MS.
the author states
that the Cuban feral dog shows great natural wildness, even when caught
quite young.

Instinct aided by reason, as in the taylor-bird1.
Taught
by parents, cows choosing food, birds singing. Instincts vary in wild
state (birds get wilder) often lost2; more perfect,—nest
without roof. These facts [only clear way] show how incomprehensibly
brain has power of transmitting intellectual operations.

Faculties3 distinct from true
instincts,—finding [way].
It must I think be admitted that habits whether congenital or acquired
by practice [sometimes] often become inherited4; instincts,
influence, equally with structure, the preservation of animals;
therefore selection must, with changing conditions tend to modify the
inherited habits of animals. If this be admitted it will be found possible that many of the strangest instincts may be thus acquired. I may
observe, without attempting definition, that an inherited habit or
trick (trick because may be born) fulfils closely what we mean by
instinct. A habit is often performed unconsciously, the strangest
habits become associated, d°. tricks, going in certain spots &c.
&c., even against will, is excited by external agencies, and looks
not to the end,—a person playing a pianoforte. If such a habit were
transmitted it would make a marvellous instinct. Let us consider some
of the most difficult cases of instincts, whether they could be possibly acquired. I do not say probably, for that belongs to our
3rd Part5, I beg this may be remembered, nor do I mean to
attempt to show exact method. I want only to show that

1 This refers to the tailor-bird
making
use of manufactured thread supplied to it, instead of thread twisted by
itself.

2Often lost applies
to instinct:
birds get wilder is printed in a parenthesis because it was
apparently added as an after-thought. Nest without roof refers
to the water-ousel omitting to vault its nest when building in a
protected situation.

3 In the MS.
of 1844
is an
interesting
discussion on faculty as distinct from instinct.

4 At this date and for long
afterwards the
inheritance of acquired characters was assumed to occur.

Every instinct must, by my theory, have been acquired
gradually by
slight changes <illegible> of former instinct, each change being
useful
to its then species. Shamming death struck me at first as remarkable
objection. I found none really sham death1, and that there
is gradation; now no one doubts that those insects which do it either
more or less, do it for some good, if then any species was led to do it
more, and then <?> escaped &c. &c.

Take migratory instincts, faculty distinct from instinct,
animals
have notion of time,—like savages. Ordinary finding way by memory, but
how does savage find way across country,—as incomprehensible to us, as
animal to them,—geological changes,—fishes in river,—case of sheep in
Spain2. Architectural instincts,—a manufacturer's employee
in making single articles extraordinary skill,—often said seem to make
it almost <illegible>, child born with such a notion of playing3,—we
can fancy tailoring acquired in same perfection,—mixture of
reason,—water-ouzel,—taylor-bird,—gradation of simple nest to most
complicated.

Bees again, distinction of faculty,—how they make a
hexagon,—Waterhouse's theory4,—the impulse to use whatever
faculty they possess,—the taylor-bird has the faculty of sewing with
beak, instinct impels him to do it.

Last case of parent feeding young with different food
(take case of
Galapagos birds, gradation from

1 The meaning is that the
attitude assumed
in shamming is not accurately like that of death.

2 This refers to the transandantes sheep
mentioned in the MS. of 1844, as having
acquired a
migratory instinct.

Hawfinch to Sylvia) selection and habit might lead old
birds to vary
taste <?> and form, leaving their instinct of feeding their young
with
same foodl,—or I see no difficulty in parents being
forced or induced to vary the food brought, and selection adapting the
young ones to it, and thus by degree any amount of diversity might be
arrived at. Although we can never hope to see the course revealed by
which different instincts have been acquired, for we have only present
animals (not well known) to judge of the course of gradation, yet once
grant the principle of habits, whether congenital or acquired by
experience, being inherited and I can see no limit to the [amount of
variation] extraordinariness <?> of the habits thus acquired.

Summing up this Division. If variation be
admitted to
occur occasionally in some wild animals, and how can we doubt it, when
we see [all] thousands <of> organisms, for whatever use taken by man,
do vary. If we admit such variations tend to be hereditary, and how can
we doubt it when we <remember> resemblances of features and
character,—disease and monstrosities inherited and endless races
produced (1200 cabbages). If we admit selection is steadily at work,
and who will doubt it, when he considers amount of food on an average
fixed and reproductive powers act in geometrical ratio. If we admit
that external conditions vary, as all geology proclaims, they have done
and are now doing,—then, if no law of nature be opposed, there must
occasionally be formed races, [slightly] differing from the parent
races. So then any such law2, none is

1 The hawfinch- and Sylvia-typesare figured in the Journal of Researches, p. 379. The
discussion of change of form in relation to change of instinct is not
clear, and I find it impossible to suggest a paraphrase.

2 I should interpret this
obscure sentence
as follows, "No such opposing law is known, but in all works on the
subject a law is (in flat contradiction to all known facts) assumed to
limit the possible amount of variation." In the Origin, the
author never limits the power of variation, as far as I know.

known, but in all works it is assumed, in <?> flat
contradiction to
all known facts, that the amount of possible variation is soon
acquired. Are not all the most varied species, the oldest domesticated:
who <would> think that horses or corn could be produced? Take dahlia
and potato, who will pretend in 5000 years1<that
great changes might not be effected>: perfectly adapted to conditions
and then again brought into varying conditions. Think what has been
done in few last years, look at pigeons, and cattle. With the amount of
food man can produce he may have arrived at limit of fatness or size,
or thickness of wool <?>, but these are the most trivial points,
but
even in these I conclude it is impossible to say we know the limit of
variation. And therefore with the [adapting] selecting power of nature,
infinitely wise compared to those of man, <I conclude> that it is
impossible to say we know the limit of races, which would be true <to
their> kind; if of different constitutions would probably be infertile
one with another, and which might be adapted in the most singular and
admirable manner, according to their wants, to external nature and to
other surrounding organisms,—such races would be species. But is there
any evidence <that> species <have> been thus produced, this is a
question wholly independent of all previous points, and which on
examination of the kingdom of nature <we> ought to answer one way or
another.

1 In Var. under Dom. Ed.
2, ii.
p. 263, the Dahlia is described as showing sensitiveness to
conditions in 1841. All the varieties of the Dahlia are said
to have arisen since 1804 (ibid. i. p. 393).

I may premise, that according to the view ordinarily
received, the
myriads of organisms peopling this world have been created by so many
distinct acts of creation. As we know nothing of the <illegible> will
of a Creator,—we can see no reason why there should exist any relation
between the organisms thus created; or again, they might be created
according to any scheme. But it would be marvellous if this scheme
should be the same as would result from the descent of groups of
organisms from [certain] the same parents, according to the
circumstances, just attempted to be developed.

With equal probability did old cosmogonists say fossils
were
created, as we now see them, with a false resemblance to living beings2;
what would the Astronomer say to the doctrine that the planets moved
<not> according to the law of gravitation, but from the Creator having
willed each separate planet to move in its particular orbit? I believe
such a proposition (if we remove all prejudices) would be as legitimate
as to admit that certain groups of living and extinct organisms, in
their distribution, in their structure and in their relations one to
another and to external conditions, agreed with the theory

1 In the original MS.
the
heading is: Part
III.; but Part II. is clearly intended; for details see the
Introduction. I have not been able to discover where § IV.
ends and § V. begins.

2 This passage corresponds
roughly to the
conclusion of the Origin, see Ed. i. p. 482, vi. p. 661.

and showed signs of common descent, and yet were created
distinct.
As long as it was thought impossible that organisms should vary, or
should anyhow become adapted to other organisms in a complicated
manner, and yet be separated from them by an impassable barrier of
sterility1, it was justifiable, even with some appearance in
favour of a common descent, to admit distinct creation according to the
will of an Omniscient Creator; or, for it is the same thing, to say
with Whewell that the beginnings of all things surpass the
comprehension of man. In the former sections I have endeavoured to show
that such variation or specification is not impossible, nay, in many
points of view is absolutely probable. What then is the evidence in
favour of it and what the evidence against it. With our imperfect
knowledge of past ages [surely there will be some] it would be strange
if the imperfection did not create some unfavourable evidence.

Give sketch of the Past,—beginning with facts appearing
hostile
under present knowledge,—then proceed to geograph. distribution,—order
of appearance,—affinities,—morphology &c., &c.

Our theory requires a very gradual introduction of new
forms2,
and extermination of the old (to which we shall revert). The
extermination of old may sometimes be rapid, but never the
introduction. In the groups descended from common parent, our theory
requires a perfect gradation not differing more than breed<s> of
cattle, or potatoes, or cabbages in forms. I do not mean that a
graduated series of animals must have existed, intermediate between
horse, mouse, tapir3, elephant [or fowl and peacock],

but that these must have had a common parent, and between
horse and
this <?> parent &c., &c., but the common parent may possibly
have differed more from either than the two do now from each other. Now
what evidence of this is there? So perfect gradation in some
departments, that some naturalists have thought that in some large
divisions, if all existing forms were collected, a near approach to
perfect gradation would be made. But such a notion is preposterous with
respect to all, but evidently so with mammals. Other naturalists have
thought this would be so if all the specimens entombed in the strata
were collected1. I conceive there is no probability whatever
of this; nevertheless it is certain all the numerous fossil forms fall
in<to>, as Buckland remarks, not present classes, families
and genera, they fall between them: so is it with new discoveries of
existing forms. Most ancient fossils, that is most separated <by> space
of time, are most apt to fall between the classes—(but
organisms from
those countries most separated by space also fall between the classes <e.g.>
Ornithorhyncus?). As far as geological discoveries <go> they tend
towards such gradation2. Illustrate it with net.
Toxodon,—tibia and fibula,—dog and otter,—but so utterly improbable is
<it>, in ex. gr. Pachydermata, to compose series as perfect
as cattle, that if, as many geologists seem to

1 The absence of intermediate
forms
between living organisms (and also as regards fossils) is discussed in
the Origin, Ed. i. pp. 279, 280, vi. p. 413. In the above
discussion there is no evidence that the author felt this difficulty so
strongly as it is expressed in the Origin, Ed. i. p. 299,—as
perhaps "the most obvious and gravest objection that can be urged
against my theory." But in a rough summary written on the back of the
penultimate page of the MS. he refers to the geological
evidence:—"Evidence, as far as it does go, is favourable, exceedingly
incomplete,—greatest difficulty on this theory. I am convinced not
insuperable." Buckland's remarks are given in the Origin, Ed.
i. p. 329, vi. p. 471.

2 That the evidence of geology,
as far as
it goes, is favourable to the theory of descent is claimed in the Origin, Ed. i. pp. 343-345, vi. pp. 490-492. For the reference to net in the following sentence, see Note 1, p. 48, of this Essay.

infer, each separate formation presents even an approach
to a
consecutive history, my theory must be given up. Even if it were
consecutive, it would only collect series of one district in our
present state of knowledge; but what probability is there that any one
formation during the immense period which has elapsed during
each period will generally present a consecutive history.
[Compare number living at one period to fossils preserved—look
at
enormous periods of time.]

Referring only to marine animals, which are obviously most
likely to
be preserved, they must live where <?> sediment (of a kind favourable
for preservation, not sand and pebble)1 is depositing
quickly and over large area and must be thickly capped, <illegible>
littoral deposits: for otherwise denudation <will destroy them>,—they
must live in a shallow space which sediment will tend to fill up,—as
movement is <in?> progress if soon brought <?> up <?> subject to
denudation,—[if] as during subsidence favourable, accords with facts of
European deposits2, but subsidence apt to destroy agents
which produce sediment3.

I believe safely inferred <that> groups of marine <?>
fossils only
preserved for future ages where sediment goes on long <and>
continuous<ly> and with rapid but not too rapid deposition in <an> area
of subsidence. In how few places in any one region like Europe will <?>
these contingencies be going on? Hence <?> in

1 See Origin, Ed. i.
p. 288, vi.
p. 422. "The remains that do become embedded, if in sand and gravel,
will, when the beds are upraised, generally be dissolved by the
percolation of rain-water."

2 The position of the following
is not
clear:—"Think of immense differences in nature of European
deposits,—without interposing new causes,—think of time required by
present slow changes, to cause, on very same area, such diverse
deposits, iron-sand, chalk, sand, coral, clay!"

3 The paragraph which ends here
is
difficult to interpret. In spite of obscurity it is easy to recognize
the general resemblance to the discussion on the importance of
subsidence given in the Origin, Ed. i. pp. 290 et seq., vi.
pp. 422 et seq.

past ages mere [gaps] pages preserved1. Lyell's
doctrine
carried to extreme,—we shall understand difficulty if it be asked:—what
chance of series of gradation between cattle by <illegible> at age
<illegible> as far back as Miocene2? We know then cattle
existed. Compare number of living,—immense duration of each
period,—fewness of fossils.

This only refers to consecutiveness of history of
organisms of each
formation.

The foregoing argument will show firstly, that formations
are
distinct merely from want of fossils <of intermediate beds>, and
secondly, that each formation is full of gaps, has been advanced to
account for fewness of preserved organisms
compared to what have lived on the world. The very same argument
explains why in older formations the organisms appear to come on and
disappear suddenly,—but in [later] tertiary not quite suddenly3,
in later tertiary gradually,—becoming rare and disappearing,—some have
disappeared within man's time. It is obvious that our theory requires
gradual and nearly uniform introduction, possibly more sudden
extermination,—subsidence of continent of Australia &c., &c.

Our theory requires that the first form which existed of
each of the
great divisions would present points intermediate between existing
ones, but immensely different. Most geologists believe Silurian4 fossils are those which first existed in the whole world,

1 See Note 3, p. 27.

2 Compare Origin, Ed.
i. p. 298,
vi. p. 437. "We shall, perhaps, best perceive the improbability of our
being enabled to connect species by numerous, fine, intermediate,
fossil links, by asking ourselves whether, for instance, geologists at
some future period will be able to prove that our different breeds of
cattle, sheep, horses, and dogs have descended from a single stock or
from several aboriginal stocks."

3 The sudden appearance of
groups of
allied species in the lowest known fossiliferous strata is discussed in
the Origin, Ed. i. p. 306, vi. p. 446. The gradual
appearance in the later strata occurs in the Origin, Ed. i.
p. 312, vi. p. 453.

not those which have chanced to be the oldest not
destroyed,—or the
first which existed in profoundly deep seas in progress of conversion
from sea to land: if they are first they <? we> give up. Not so Hutton
or Lyell: if first reptile1 of Red Sandstone <?> really was
first which existed: if Pachyderm2 of Paris was first which
existed: fish of Devonian: dragon fly of Lias: for we cannot suppose
them the progenitors: they agree too closely with existing divisions.
But geologists consider Europe as <?> a passage from sea to island <?>
to continent (except Wealden, see Lyell). These animals therefore, I
consider then mere introduction <?> from continents long since
submerged.

Finally, if views of some geologists be correct, my theory
must be
given up. [Lyell's views, as far as they go, are in favour,
but they go so little in favour, and so much more is required, that it
may <be> viewed as objection.] If geology present us with mere pages in
chapters, towards end of <a> history, formed by tearing out bundles of
leaves, and each page illustrating merely a small portion of the
organisms of that time, the facts accord perfectly with my theory3.

1 I have interpreted as Sandstone a
scrawl which I first read as Sea; I have done so at the
suggestion of Professor Judd, who points out that "footprints in the
red sandstone were known at that time, and geologists were not then
particular to distinguish between Amphibians and Reptiles."

2 This refers to Cuvier's
discovery of Palæotherium &c. at Montmartre.

3 This simile is more fully
given in the Origin, Ed. i. p. 310, vi. p. 452. "For my part, following out Lyell's
metaphor, I look at the natural geological record, as a history of the
world imperfectly kept, and written in a changing dialect; of this
history we possess the last volume alone, relating only to two or three
countries. Of this volume, only here and there a short chapter has been
preserved; and of each page, only here and there a few lines. Each word
of the slowly-changing language, in which the history is supposed to be
written, being more or less different in the interrupted succession of
chapters, may represent the apparently abruptly changed forms of life,
entombed in our consecutive, but widely separated formations."
Professor Judd has been good enough to point out to me, that Darwin's
metaphor is founded on the comparison of geology to history in Ch. i.
of the Principles of Geology, Ed. i. 1830, vol. i. pp. 1-4.
Professor Judd has also called my attention to another passage,—Principles, Ed. i. 1833, vol. iii. p. 33, when Lyell imagines an historian
examining "two buried cities at the foot of Vesuvius, immediately
superimposed upon each

Extermination. We have seen that in later
periods the
organisms have disappeared by degrees and [perhaps] probably by degrees
in earlier, and I have said our theory requires it. As many naturalists
seem to think extermination a most mysterious circumstance1 and call in astonishing agencies, it is well to recall what we have
shown concerning the struggle of nature. An exterminating agency is at
work with every organism: we scarcely see it: if robins would increase
to thousands in ten years how severe must the process be. How
imperceptible a small increase: fossils become rare: possibly sudden
extermination as Australia, but as present means very slow and many
means of escape, I shall doubt very sudden exterminations. Who can
explain why some species abound more,—why does marsh titmouse, or
ring-ouzel, now little change,—why is one sea-slug rare and another
common on our coasts,—why one species of Rhinoceros more than
another,—why is <illegible> tiger of India so rare? Curious and general
sources of error, the place of an organism is instantly filled up.

We know state of earth has changed, and as earthquakes and
tides go
on, the state must change,—many geologists believe a slow gradual
cooling. Now let us see in accordance with principles of [variation]
specification explained in Sect. II. how species would
probably be
introduced and how such results accord with what is known.

other." The historian would discover that
the
inhabitants of the lower town were Greeks while those of the upper one
were Italians. But he would be wrong in supposing that there had been a
sudden change from the Greek to the Italian language in Campania. I
think it is clear that Darwin's metaphor is partly taken from this
passage. See for instance (in the above passage from the Origin)
such
phrases as "history...written in a changing dialect"—"apparently
abruptly changed forms of life." The passage within [ ] in the above
paragraph:—"Lyell's views as far as they go &c.," no doubt refers,
as Professor Judd points out, to Lyell not going so far as Darwin on
the question of the imperfection of the geological record.

The first fact geology proclaims is immense number of
extinct forms,
and new appearances. Tertiary strata leads to belief, that forms
gradually become rare and disappear and are gradually supplied by
others. We see some forms now becoming rare and disappearing, we know
of no sudden creation: in older periods the forms appear to
come in suddenly, scene shifts: but even here Devonian, Permian &c.
[keep on supplying new links in chain]—Genera
and higher forms come on
and disappear, in same way leaving a species on one or more stages
below that in which the form abounded.

<GEOGRAPHICAL DISTRIBUTION.>

§ VI. Let us consider the
absolute state of
distribution of organisms of earth's face.

Referring chiefly, but not exclusively (from difficulty of
transport, fewness, and the distinct characteristics of groups) to
Mammalia; and first considering the three or four main [regions]
divisions; North America, Europe, Asia, including greater part of E.
Indian Archipelago and Africa are intimately allied. Africa most
distinct, especially most southern parts. And the Arctic regions, which
unite N. America, Asia and Europe, only separated (if we travel one way
by Behring's St.) by a narrow strait, is most intimately allied, indeed
forms but one restricted group. Next comes S. America,—then Australia,
Madagascar (and some small islands which stand very remote from the
land). Looking at these main divisions separately, the organisms vary
according to changes in condition1 of different parts. But
besides this, barriers of every kind seem to separate

1 In the Origin, Ed.
i. p. 346,
vi. p. 493, the author begins his discussion on geographical
distribution by minimising the effect of physical conditions. He lays
great stress on the effect of barriers, as in the present
Essay.

regions in a greater degree than proportionally to the
difference of
climates on each side. Thus great chains of mountains, spaces of sea
between islands and continents, even great rivers and deserts. In fact
the amount <of> difference in the organisms bears a certain, but not
invariable relation to the amount of physical difficulties to transit1.

There are some curious exceptions, namely, similarity of
fauna of
mountains of Europe and N. America and Lapland. Other cases just <the>
reverse, mountains of eastern S. America, Altai (?), S. India (?)2:
mountain summits of islands often eminently peculiar. Fauna generally
of some islands, even when close, very dissimilar, in others very
similar. [I am here led to observe one or more centres of creation3.]

The simple geologist can explain many of the foregoing
cases of
distribution. Subsidence of a continent in which free means of
dispersal, would drive the lowland plants up to the mountains, now
converted into islands, and the semi-alpine plants would take place of
alpine, and alpine be destroyed, if mountains originally were not of
great height. So we may see, during gradual changes4 of
climate on a continent, the propagation of species would vary and adapt
themselves to small changes

1 Note in the original, "Would
it be more
striking if we took animals, take Rhinoceros, and study their habitats?"

2 Note by Mr A. R. Wallace. "The
want of
similarity referred to, is, between the mountains of Brazil and Guiana
and those of the Andes. Also those of the Indian peninsula as compared
with the Himalayas. In both cases there is continuous intervening land.

"The islands referred to were, no doubt,
the
Galapagos for dissimilarity from S. America; our own Islands as
compared with Europe, and perhaps Java, for similarity with continental
Asia."

3 The arguments against multiple
centres
of creation are given in the Origin, Ed. i. p. 352, vi. p.
499.

4 In the Origin, Ed.
i. p. 366,
vi. p. 516, the author does not give his views on the distribution of
alpine plants as original but refers to Edward Forbes' work (Geolog.
Survey Memoirs, 1846). In his autobiography, Darwin refers to
this. "I was forestalled" he says, "in only one important point, which
my vanity has always made me regret." (Life and Letters, i.
p. 88.)

causing much extermination1. The mountains of
Europe were
quite lately covered with ice, and the lowlands probably partaking of
the Arctic climate and Fauna. Then as climate changed, arctic fauna
would take place of ice, and an inundation of plants from different
temperate countries <would> seize the lowlands, leaving islands of
arctic forms. But if this had happened on an island, whence could the
new forms have come,—here the geologist calls in creationists. If
island formed, the geologist will suggest <that> many of the forms
might have been borne from nearest land, but if peculiar, he calls in
creationist,—as such island rises in height &c., he still more
calls in creation. The creationist tells one, on a <illegible> spot the
American spirit of creation makes Orpheus and Tyrannus and
American doves, and in accordance with past and extinct forms, but no
persistent relation between areas and distribution,
Geologico-Geograph.-Distribution.

1 <The following is written on
the back of
a page of the MS.> Discuss one or more centres of
creation: allude
strongly to facilities of dispersal and amount of geological change:
allude to mountain-summits afterwards to be referred to. The
distribution varies, as everyone knows, according to adaptation,
explain going from N. to S. how we come to fresh groups of
species in the same general region, but besides this we find
difference, according to greatness of barriers, in greater proportion
than can be well accounted for by adaptation. <On representive species
see Origin, Ed. i. p. 349, vi. p. 496.> This very striking
when we think of cattle of Pampas, plants <?> &c. &c. Then go
into discussion; this holds with 3 or 4 main divisions as well as the
endless minor ones in each of these 4 great ones: in these I chiefly
refer to mammalia &c. &c. The similarity of type, but not in
species, in same continent has been much less insisted on than the
dissimilarity of different great regions generically: it is more
striking.

<I have here omitted an incomprehensible
sentence.> Galapagos Islands,
Tristan d'Acunha, volcanic islands covered with craters we
know lately did not support any organisms. How unlike these islands in
nature to neighbouring lands. These facts perhaps more striking than
almost any others. [Geology apt to affect geography therefore we ought
to expect to find the above.] Geological-geographical distribution. In
looking to past times we find Australia equally distinct. S. America
was distinct, though with more forms in common. N. America its nearest
neighbour more in common,—in
some respects more, in some less allied
to Europe. Europe we find <?> equally European. For Europe is now part
of Asia though not <illegible>. Africa unknown,—examples, Elephant,
Rhinoceros, Hippopotamus, Hyaena. As geology destroys geography we
cannot be surprised in going far back we find Marsupials and Edentata
in Europe: but geology destroys geography.

Now according to analogy of domesticated animals let us
see what
would result. Let us take case of farmer on Pampas, where everything
approaches nearer to state of nature. He works on organisms having
strong tendency to vary: and he knows <that the> only way to make a
distinct breed is to select and separate. It would be useless to
separate the best bulls and pair with best cows if their offspring run
loose and bred with the other herds, and tendency to reversion not
counteracted; he would endeavour therefore to get his cows on islands
and then commence his work of selection. If several farmers in
different rincons1were to set to work,
especially if with different objects, several breeds would soon be
produced. So would it be with horticulturist and so history of every
plant shows; the number of varieties2 increase in proportion
to care bestowed on their selection and, with crossing plants,
separation. Now, according to this analogy, change of external
conditions, and isolation either by chance landing <of> a form on an
island, or subsidence dividing a continent, or great chain of
mountains, and the number of individuals not being numerous will best
favour variation and selection3. No doubt change could be
effected in same country without any barrier by long continued
selection on one species: even in case of a plant not capable of
crossing would easier get possession and solely

1Rincon in Spanish
means a nook or corner, it is here probably used to mean a small farm.

2 The following is written
across the
page: "No one would expect a set of similar varieties to be produced in
the different countries, so species different."

3 <The following passage seems
to have
been meant to follow here.> The parent of an organism, we may generally
suppose to be in less favourable condition than the selected offspring
and therefore generally in fewer numbers. (This is not borne out by
horticulture, mere hypothesis; as an organism in favourable conditions
might by selection be adapted to still more favourable conditions.)

Barrier would further act in preventing
species
formed in one part migrating to another part.

occupy an island1. Now we can at once see that
<if> two
parts of a continent isolated, new species thus generated in them,
would have closest affinities, like cattle in counties of England: if
barrier afterwards destroyed one species might destroy the other or
both keep their ground. So if island formed near continent, let it be
ever so different, that continent would supply inhabitants, and new
species (like the old) would be allied with that continent. An island
generally very different soil and climate, and number and order of
inhabitants supplied by chance, no point so favourable for generation
of new species2,—especially the mountains, hence, so it is.
As isolated mountains formed in a plain country (if such happens) is an
island. As other islands formed, the old species would spread and thus
extend and the fauna of distant island might ultimately meet and a
continent formed between them. No one doubts continents formed by
repeated elevations and depressions3. In looking backwards,
but not so far that all geographical boundaries are destroyed, we can
thus at once see why existing forms are related to the extinct in the
same manner as existing ones are in some part of existing continent. By
chance we might even have one or two absolute parent fossils.

The detection of transitional forms would be rendered more
difficult
on rising point of land.

The distribution therefore in the above enumer-

1 <The following notes occur on
the back
of the page.> Number of species not related to capabilities of the
country: furthermore not always those best adapted, perhaps explained
by creationists by changes and progress. <See p. 34, note 1.>

Although creationists can, by help of
geology,
explain much, how can he explain the marked relation of past and
present in same area, the varying relation in other cases, between past
and present, the relation of different parts of same great area. If
island, to adjoining continent, if quite different, on mountain
summits,—the number of individuals not being related to capabilities,
or how &c.—our theory, I believe, can throw much light and all
facts accord.

ated points, even the trivial ones, which on any other
<theory?> can
be viewed as so many ultimate facts, all follow <in> a simple manner on
the theory of the occurrence of species by <illegible> and being
adapted by selection to <illegible>, conjoined with their power of
dispersal, and the steady geographico-geological changes which are now
in progress and which undoubtedly have taken place. Ought to state the
opinion of the immutability of species and the creation by so many
separate acts of will of the Creator1.

1 <From the back of MS.>
Effect of climate
on stationary island and on continent, but continent once island.
Moreover repeated oscillations fresh diffusion when non-united, then
isolation, when rising again immigration prevented, new habitats
formed, new species, when united free immigration, hence uniform
characters. Hence more forms <on?> the island. Mountain summits. Why
not true species. First let us recall in Part I, conditions of
variation: change of conditions during several generations, and if
frequently altered so much better [perhaps excess of food]. Secondly,
continued selection [while in wild state]. Thirdly, isolation in all or
nearly all,—as well to recall advantages of.

[In continent, if we look to terrestrial
animal, long
continued change might go on, which would only cause change in
numerical number <? proportions>: if continued long enough might
ultimately affect all, though to most continents <there is> chance of
immigration. Some few of whole body of species must be long affected
and entire selection working same way. But here isolation absent,
without barrier, cut off such <illegible>. We can see advantage of
isolation. But let us take case of island thrown up by volcanic agency
at some distances, here we should have occasional visitants, only in
few numbers and exposed to new conditions and <illegible> more
important,—a quite new grouping of organic beings, which would open out
new sources of subsistence, or <would> control <?> old ones. The number
would be few, can old have the very best opportunity. <The conquest of
the indigenes by introduced organisms shows that the indigenes were not
perfectly adapted, see Origin, Ed. i. p. 390.> Moreover as
the island continued changing,—continued slow changes, river, marshes,
lakes, mountains &c. &c., new races as successively formed and
a fresh occasional visitant.

If island formed continent, some species
would emerge
and immigrate. Everyone admits continents. We can see why Galapagos and
C. Verde differ <see Origin, Ed. i. p. 398>], depressed and
raised. We can see from this repeated action and the time required for
a continent, why many more forms than in New Zealand <see Origin,
Ed. i. p. 389 for a comparison between New Zealand and the Cape> no
mammals or other classes <see however, Origin, Ed. i. p. 393
for the case of the frog>. We can at once see how it comes when there
has been an old channel of migration,—Cordilleras; we can see why
Indian Asiatic Flora,—[why species] having a wide range gives better
chance of some arriving at new points and being selected, and adapted
to new ends. I need hardly remark no necessity for change.

Looking now to the affinities of organisms, without
relation to
their distribution, and taking all fossil and recent, we see the
degrees of relationship are of different degrees and
arbitrary,—sub-genera,—genera,—sub-families,
families, orders and
classes and kingdoms. The kind of classification which everyone feels
is most correct is called the natural system, but no can define this.
If we say with Whewell <that we have an> undefined instinct of the
importance of organs1, we have no means in lower

Finally, as continent (most extinction <?> during
formation of
continent) is formed after repeated elevation and depression, and
interchange of species we might foretell much extinction, and that the
survivor would belong to same type, as the extinct, in same manner as
different part of same continent, which were once separated by space as
they are by time <see Origin, Ed. i. pp. 339 and 349>.

As all mammals have descended from one stock, we ought to
expect
that every continent has been at some time connected, hence
obliteration of present ranges. I do not mean that the fossil mammifers
found in S. America are the lineal successors <ancestors> of the
present forms of S. America: for it is highly improbable that more than
one or two cases (who will say how many races after Plata bones) should
be found. I believe this from numbers, who have lived,—mere <?> chance
of fewness. Moreover in every case from very existence of genera and
species only few at one time will leave progeny, under form of new
species, to distant ages; and the more distant the ages the fewer the
progenitors. An observation may be here appended, bad chance of
preservation on rising island, the nurseries of new species, appeal to
experience <see Origin, Ed. i. p. 292>. This observation may
be extended, that in all cases, subsiding land must be, in early
stages, less favourable to formation of new species; but it will
isolate them, and then if land recommences rising how favourable. As
preoccupation is bar to diffusion to species, so would it be to a
selected variety. But it would not be if that variety was better fitted
to some not fully occupied station; so during elevation or the
formation of new stations, is scene for new species. But during
elevation not favourable to preservation of fossil (except in caverns
<?>); when subsidence highly favourable in early stages to preservation
of fossils; when subsidence, less sediment. So that our strata, as
general rule will be the tomb of old species (not undergoing any
change) when rising land the nursery. But if there be vestige will
generally be preserved to future ages, the new ones will not be
entombed till fresh subsidence supervenes. In this long gap we shall
have no record: so that wonderful if we should get transitional forms.
I do not mean every stage, for we cannot expect that, as before shown,
until geologists will be prepared to say that although under
unnaturally favourable condition we can trace in future ages short-horn
and Herefordshire <see note 2, p. 26>.

1 After "organs" is inserted,
apparently as an afterthought:—"no, and instance metamorphosis,
afterwards explicable."

animals of saying which is most important, and yet
everyone feels
that some one system alone deserves to be called natural. The true
relationship of organisms is brought before one by considering
relations of analogy, an otter-like animal amongst mammalia and an
otter amongst marsupials. In such cases external resemblance and habit
of life and the final end of whole organization very strong,
yet no relation1. Naturalists cannot avoid these terms of
relation and affinity though they use them metaphorically. If used in
simple earnestness the natural system ought to be a genealogical <one>;
and our knowledge of the points which are most easily affected in
transmission are those which we least value in considering the natural
system, and practically when we find they do vary we regard them of
less value2. In classifying varieties the same language is
used and the same kind of division: here also (in pine-apple)3 we talk of the natural classification, overlooking similarity of the
fruits, because whole plant differs. The origin of sub-genera, genera,
&c., &c., is not difficult on notion of genealogical
succession, and accords with what we know of similar gradations of
affinity in domesticated organisms. In the same region the organic
beings are <illegible> related to each other and the external
conditions in many physical respects are allied4 and their
differences of same kind, and therefore when a new species has been
selected and has obtained a place in the economy of nature, we

1 For analogical resemblances
see Origin,
Ed. i. p. 427, vi. p. 582.

2 "Practically when naturalists
are at
work, they do not trouble themselves about the physiological value of
the characters....If they find a character nearly uniform,...they use
it as one of high value," Origin, Ed. i. p. 417, vi. p. 573.

3 "We are cautioned...not to
class two
varieties of the pine-apple together, merely because their fruit,
though the most important part, happens to be nearly identical," Origin, Ed. i. p. 423, vi. p. 579.

4 The whole of this passage is
obscure,
but the text is quite clear, except for one illegible word.

may suppose that generally it will tend to extend its
range during
geographical changes, and thus, becoming isolated and exposed to new
conditions, will slightly alter and its structure by selection become
slightly remodified, thus we should get species of a sub-genus and
genus,—as varieties of merino-sheep,—varieties of British and Indian
cattle. Fresh species might go on forming and others become extinct and
all might become extinct, and then we should have <an> extinct genus; a
case formerly mentioned, of which numerous cases occur in
Palæontology. But more often the same advantages which caused the new
species to spread and become modified into several species would favour
some of the species being preserved: and if two of the species,
considerably different, each gave rise to group of new species, you
would have two genera; the same thing will go on. We may look at case
in other way, looking to future. According to mere chance every
existing species may generate another, but if any species, A, in
changing gets an advantage and that advantage (whatever it may be,
intellect, &c., &c., or some particular structure or
constitution) is inherited1, A will be the progenitor of
several genera or even families in the hard struggle of nature. A will
go on beating out other forms, it might come that A would people
earth,—we may now not have one descendant on our globe of the one or
several original creations2. External conditions air, earth,
water being same3 on globe, and the communication not being
perfect, organisms of widely different descent might become adapted to

1 <The exact position of the
following
passage is uncertain:> "just as it is not likely every present breed of
fancy birds and cattle will propagate, only some of the best."

2 This suggests that the author
was not
far from the principle of divergence on which he afterwards laid so
much stress. See Origin, Ed. i. p. 111, vi. p. 134, also Life
and Letters, i. p. 84.

3 That is to say the same
conditions
occurring in different parts of the globe.

the same end and then we should have cases of analogy1,
[they might even tend to become numerically representative]. From this
often happening each of the great divisions of nature would have their
representative eminently adapted to earth, to <air>2, to
water, and to these in <illegible> and then these great divisions would
show numerical relations in their classification.

§ VIII.
UNITY [OR
SIMILARITY] OF TYPE IN THE GREAT CLASSES.

Nothing more wonderful in Nat. Hist, than looking at the
vast number
of organisms, recent and fossil, exposed to the most diverse
conditions, living in the most distant climes, and at immensely remote
periods, fitted to wholely different ends, yet to find large groups
united by a similar type of structure. When we for instance see bat,
horse, porpoise-fin, hand, all built on same structure3,
having bones4 with same name, we see there is some deep bond
of union between them5, to illustrate this is the foundation
and objects <?> <of> what is called the Natural System; and which is
foundation of distinction <?> of true and adaptive characters6.
Now this wonderful fact of hand, hoof, wing, paddle and claw being the
same, is at once explicable on the principle of some parent-forms,
which might either be <illegible> or walking animals, becoming through
infinite number of small

1 The position of the following
is
uncertain, "greyhound and racehorse have an analogy to each other." The
same comparison occurs in the Origin, Ed. i. p. 427, vi. p.
583.

2Air is evidently
intended; in
the MS. water is written twice.

3 Written between the lines
occurs:—"extend to birds and other classes."

4 Written between the lines
occurs:—"many
bones merely represented."

5 In the Origin, Ed.
i. p. 434,
vi. p. 595, the term morphology is taken as including unity
of type. The paddle of the porpoise and the wing of the bat are
there used as instances of morphological resemblance.

selections adapted to various conditions. We know that
proportion,
size, shape of bones and their accompanying soft parts vary, and hence
constant selection would alter, to almost any purpose <?> the framework
of an organism, but yet would leave a general, even closest similarity
in it.

[We know the number of similar parts, as vertebræ and
ribs can
vary, hence this also we might expect.] Also <if> the changes carried
on to a certain point, doubtless type will be lost, and this is case
with Plesiosaurus1. The unity of type in past and present
ages of certain great divisions thus undoubtedly receives the simplest
explanation.

There is another class of allied and almost identical
facts,
admitted by the soberest physiologists, [from the study of a certain
set of organs in a group of organisms] and refers <? referring> to a
unity of type of different organs in the same individual, denominated
the science of "Morphology." The <? this> discovered by beautiful and
regular series, and in the case of plants from monstrous changes, that
certain organs in an individual are other organs metamorphosed. Thus
every botanist considers petals, nectaries, stamens, pistils, germen as
metamorphosed leaf. They thus explain, in the most lucid manner, the
position and number of all parts of the flower, and the curious
conversion under cultivation of one part into another. The complicated
double set of jaws and palpi of crustaceans2, and all
insects are considered as metamorphosed <limbs> and to see the series
is to admit this phraseology. The skulls of the vertebrates are
undoubtedly composed of three metamorphosed vertebræ; thus we can
understand the strange form of

1 In the Origin, Ed.
i. p. 436,
vi. p. 598, the author speaks of the "general pattern" being obscured
in
the paddles of "extinct gigantic sea-lizards."

the separate bones which compose the casket holding man's
brain.
These1 facts differ but slightly from those of last section,
if with wing, paddle, hand and hoof, some common structure was yet
visible, or could be made out by a series of occasional monstrous
conversions, and if traces could be discovered of <the> whole having
once existed as walking or swimming instruments, these organs would be
said to be metamorphosed, as it is they are only said to exhibit a
common type.

This distinction is not drawn by physiologists, and is
only implied
by some by their general manner of writing. These facts, though
affecting every organic being on the face of the globe, which has
existed, or does exist, can only be viewed by the Creationist as
ultimate and inexplicable facts. But this unity of type through the
individuals of a group, and this metamorphosis of the same organ into
other organs, adapted to diverse use, necessarily follows on the theory
of descent2. For let us take case of Vertebrata, which if3 they descended from one parent and by this theory all the Vertebrata
have been altered by slow degrees, such as we see in domestic animals.
We know that proportions alter, and even that occasionally numbers of
vertebræ alter, that parts become soldered, that parts are lost, as
tail and toes, but we know <that?> here we can see that possibly a
walking organ might <?> be converted into swimming or into a gliding
organ and so on to a flying organ. But such gradual changes would not
alter the unity of type in their descendants, as parts lost and
soldered and vertebræ.

1 The following passage seems to
have been
meant to precede the sentence beginning "These facts":—"It is evident,
that when in each individual species, organs are metamorph. a unity of
type extends."

2 This is, I believe, the first
place in
which the author uses the words "theory of descent."

3 The sentence should probably
run, "Let
us take the case of the vertebrata: if we assume them to be descended
from one parent, then by this theory they have been altered &c."

But we can see that if this carried to extreme, unity
lost,—Plesiosaurus. Here we have seen the same organ is formed <?>
<for> different purposes <ten words illegible>: and if, in several
orders of vertebrata, we could trace origin <of> spinous processes and
monstrosities &c. we should say, instead of there existing a unity
of type, morphology1, as we do when we trace the head as
being the vertebræ metamorphosed. Be it observed that Naturalists, as
they use terms of affinity without attaching real meaning, here also
they are obliged to use metamorphosis, without meaning that any parent
of crustacean was really an animal with as many legs as crustacean has
jaws. The theory of descent at once explains these wonderful facts.

Now few of the physiologists who use this language really
suppose
that the parent of insect with the metamorphosed jaw, was an insect
with [more] so many legs, or that the parent of flowering plants,
originally had no stamens, or pistils or petals, but some other means
of propagation,—and so in other cases. Now according to our theory
during the infinite number of changes, we might expect that an organ
used for a purpose might be used for a different one by his descendant,
as must have been the case by our theory with the bat, porpoise, horse,
&c., which are descended from one parent. And if it so chanced that
traces of the former use and structure of the part should be retained,
which is manifestly possible if not probable, then we should have the
organs, on which morphology is founded and which instead of being
metaphorical becomes plain and <and instead of being> utterly
unintelligible becomes simple matter of fact2.

1 That is "we should call it a
morphological fact."

2 In the Origin, Ed.
i. p. 438,
vi. p. 602, the author, referring to the expressions used by
naturalists in regard to morphology and metamorphosis, says "On my view
these terms may be used literally."

<Embryology.> This general unity of type in great
groups of
organisms (including of course these morphological cases) displays
itself in a most striking manner in the stages through which the fœtus
passes1. In early stage, the wing of bat, hoof, hand, paddle
are not to be distinguished. At a still earlier <stage> there is no
difference between fish, bird, &c. &c. and mammal. It is not
that they cannot be distinguished, but the arteries2 <illegible>. It is not true that one passes through the form of a lower
group, though no doubt fish more nearly related to fœtal state3.

This similarity at the earliest stage is remarkably shown
in the
course of the arteries which become greatly altered, as fœtus advances
in life and assumes the widely different course and number which
characterize full-grown fish and mammals. How wonderful that in egg, in
water or air, or in womb of mother, artery4 should run in
same course.

Light can be thrown on this by our theory.
The
structure of each organism is chiefly adapted to the sustension of its
life, when full-grown, when it has to feed itself and propagate5.
The structure of a kitten is quite in secondary degree adapted to its
habits, whilst fed by its mother's milk and prey. Hence variation in
the structure of the full-grown species will chiefly determine
the preservation of a

1 See Origin, Ed. i.
p. 439, vi.
p. 605.

2 In the Origin, Ed.
i. p. 440,
vi. p. 606, the author argues that the "loop-like course of the
arteries" in the vertebrate embryo has no direct relation to the
conditions of existence.

3 The following passages are
written
across the page:—"They pass through the same phases, but some,
generally called the higher groups, are further metamorphosed.

5 The following: "Deaths of
brothers <when> old by same peculiar disease" which is written between
the lines
seems to have been a memorandum which is expanded a few lines lower. I
believe the case of the brothers came from Dr R. W. Darwin.

species now become ill-suited to its habitat, or rather
with a
better place opened to it in the economy of Nature. It would not matter
to the full-grown cat whether in its young state it was more or less
eminently feline, so that it become so when full-grown. No doubt most
variation, (not depending on habits of life of individual) depends on
early change1and
we must suspect that at whatever
time of life the alteration of fœtus is effected, it tends to appear at
same period. When we <see> a tendency to particular disease in old age
transmitted by the male, we know some effect is produced during
conception, on the simple cell of ovule, which will not produce its
effect till half a century afterwards and that effect is not visible2.
So we see in grey-hound, bull-dog, in race-horse and cart-horse, which
have been selected for their form in full-life, there is much less (?)
difference in the few first days after birth3, than when
full-grown: so in cattle, we see it clearly in cases of cattle, which
differ obviously in shape and length of horns. If man were during
10,000 years to be able to select, far more diverse animals from horse
or cow, I should expect there would be far less differences in the very
young and fœtal state: and this, I think, throws light on above
marvellous fact. In larvæ, which have long life selection, perhaps,
does much,—in the pupa not so much4. There is no

1 See the discussion to this
effect in the Origin, Ed. i. pp. 443-4, vi. p. 610. The author there makes
the distinction between a cause affecting the germ-cell and the
reaction occurring at a late period of life.

2Possibly the
sentence was
meant to end "is not visible till then."

3 See Origin, Ed. i.
pp. 444-5,
vi. p. 611. The query appended to much less is justified,
since measurement was necessary to prove that the grey-hound and
bulldog
puppies had not nearly acquired "their full amount of proportional
difference."

4 <The following discussion,
from the back
of the page, is in large measure the same as the text.> I think light
can be thrown on these facts. From the following peculiarities being
hereditary, [we know that some change in the germinal vesicle is
effected, which will only betray itself years after] diseases—man,
goitre, gout, baldness, fatness, size, [longevity <illegible> time of

object gained in varying form &c. of fœtus (beyond
certain
adaptations to mother's womb) and therefore selection will not further
act on it, than in giving to its changing tissues a tendency to certain
parts afterwards to assume certain forms.

Thus there is no power to change the course of

reproduction, shape of horns, case of old
brothers
dying of same disease]. And we know that the germinal vesicle must have
been affected, though no effect is apparent or can be apparent till
years afterwards,—no more apparent than when these peculiarities appear
by the exposure of the full-grown individual. <That is, "the young
individual is as apparently free from the hereditary changes which will
appear later, as the young is actually free from the changes produced
by exposure to certain conditions in adult life."> So that when we see
a variety in cattle, even if the variety be due to act of reproduction,
we cannot feel sure at what period this change became apparent. It may
have been effected during early age of free life <or> fœtal existence,
as monsters show. From arguments before used, and crossing, we may
generally suspect in germ; but I repeat it does not follow, that the
change should be apparent till life fully developed; any more than
fatness depending on heredity should be apparent during early
childhood, still less during fœtal existence. In case of horns of
cattle, which when inherited must depend on germinal vesicle, obviously
no effect till cattle full-grown. Practically it would appear that the
[hereditary] peculiarities characterising our domestic races, therefore
resulting from vesicle, do not appear with their full characters in
very early states; thus though two breeds of cows have calves different
they are not so different,—grey-hound and bull-dog. And this is what is
<to> be expected, for man is indifferent to characters of young animals
and hence would select those full-grown animals which possessed the
desirable characteristics. So that from mere chance we might expect
that some of the characters would be such only as became fully apparent
in mature life. Furthermore we may suspect it to be a law, that at
whatever time a new character appears, whether from vesicle, or effects
of external conditions, it would appear at corresponding time <see Origin,
Ed. i. p. 444>. Thus diseases appearing in old age produce children
with d°.,—early maturity,—longevity,—old men, brothers, of same
disease—young children of
d°. I said men do not select for quality of
young,—calf with big bullocks. Silk-worms, peculiarities which, appear
in caterpillar state or cocoon state, are transmitted to corresponding
states. The effect of this would be that if some peculiarity was born
in a young animal, but never exercised, it might be inherited in young
animal; but if exercised that part of structure would be increased and
would be inherited in corresponding time of life after such training.

I have said that man selects in full-life,
so would
it be in Nature. In struggle of existence, it matters nothing to a
feline animal, whether kitten eminently feline, as long as it sucks.
Therefore natural selection would act equally well on character which
was fully <developed> only in full age. Selection could tend to alter
no character in fœtus, (except relation to mother) it would alter less
in young state (putting on one side larva condition) but alter every
part in full-grown condition. Look to a fœtus and its parent, and
again after ages fœtus and its <i.e. the above mentioned parents>
descendant; the parent more variable <?> than fœtus, which explains all.

the arteries, as long as they nourish the fœtus; it is
the
selection of slight changes which supervene at any time during
<illegible> of life.

The less differences of foetus,—this has obvious meaning
on this
view: otherwise how strange that a [monkey] horse, a man, a bat should
at one time of life have arteries, running in a manner, which is only
intelligibly useful in a fish! The natural system being on theory
genealogical, we can at once see, why fœtus, retaining traces of the
ancestral form, is of the highest value in classification.

§ IX. <ABORTIVE ORGANS.>

There is another grand class of facts relating to what are
called
abortive organs. These consist of organs which the same reasoning power
that shows us how beautifully these organs in some cases are adapted to
certain end, declares in other cases are absolutely useless. Thus teeth
in Rhinoceros1, whale, narwhal,—bone on tibia, muscles which
do not move,—little bone of wing of Apteryx,—bone representing
extremities in some snake,—little wings within <?> soldered cover of
beetles,—men and bulls, mammæ: filaments without anthers in plants,
mere scales representing petals in others, in feather-hyacinth whole
flower. Almost infinitely numerous. No one can reflect on these without
astonishment, can anything be clearer than that wings are to fly and
teeth <to bite>, and yet we find these organs perfect in every detail
in situations where they cannot possibly be of their normal use2.

to above structure (as invariable as all other
parts1)
from their absolute similarity to monstrous cases, where from accident, certain organs are not developed; as infant without arms or
fingers with mere stump representing them: teeth represented by mere
points of ossification: headless children with mere button,—viscera
represented by small amorphous masses, &c.,—the tail by mere
stump,— a solid horn by minute hanging one2. There is a
tendency in all these cases, when life is preserved, for such
structures to become hereditary. We see it in tailless dogs and cats.
In plants we see this strikingly,—in Thyme, in Linum flavum,—stamen
in Geranium pyrenaicum3. Nectaries abort into
petals in
Columbine <Aquilegia>, produced from some accident and then
become hereditary, in some cases only when propagated by buds, in other
cases by seed. These cases have been produced suddenly by accident in
early growth, but it is part of law of growth that when any organ is
not used it tends to diminish (duck's wing4?) muscles of
dog's ears, <and of> rabbits, muscles wither, arteries grow up. When
eye born defective, optic nerve (Tuco Tuco) is atrophied. As every part
whether useful or not (diseases, double flowers) tends to be
transmitted to offspring, the origin of abortive organs whether
produced at the birth or slowly acquired is easily understood in
domestic races of organisms: [a struggle between the atrophy and
hereditariness. Abortive organs in domestic races.] There will always
be a struggle between atrophy of an organ rendered useless, and

1 I imagine the meaning to be
that
abortive organs are specific characters in contrast to monstrosities.

hereditariness1. Because we can understand the
origin of
abortive organs in certain cases, it would be wrong to conclude
absolutely that all must have had same origin, but the strongest
analogy is in favour of it. And we can by our theory, for during
infinite changes some organ, we might have anticipated, would have
become useless. <We can> readily explain the fact, so astounding on any
other view, namely that organs possibly useless have been formed often
with the same exquisite care as when of vital importance.

Our theory, I may remark would permit an organ <to> become
abortive
with respect to its primary use, to be turned to any other purpose, (as
the buds in a cauliflower) thus we can see no difficulty in bones of
male marsupials being used as fulcrum of muscles, or style of marygold2,—indeed
in one point of view, the heads of [vertebrated] animal may be said to
be abortive vertebræ turned into other use: legs of some crustacea
abortive jaws, &c., &c. De Candolle's analogy of table covered
with dishes3.

<The following passage was possibly intended to be
inserted here.>
Degradation and complication see Lamarck: no tendency to perfection: if
room, [even] high organism would have greater power in beating lower
one, thought <?> to be selected for a degraded end.

1 The words vis medicatrix are
inserted after "useless," apparently as a memorandum.

2 In the male florets of certain
Compositæ the style functions merely as a piston for forcing out the
pollen.

3 <On the back of the page is
the
following.> If abortive organs are a trace preserved by hereditary
tendency, of organ in ancestor of use, we can at once see why important
in natural classification, also why more plain in young animal because,
as in last section, the selection has altered the old animal most. I
repeat, these wondrous facts, of parts created for no use in past and
present time, all can by my theory receive simple explanation; or they
receive none and we must be content with some such empty metaphor, as
that of De Candolle, who compares creation to a well covered table, and
says abortive organs may be compared to the dishes (some should be
empty) placed symmetrically!

Let us recapitulate the whole <?> <of> these latter
sections by
taking case of the three species of Rhinoceros, which inhabit Java,
Sumatra, and mainland of Malacca or India. We find these three close
neighbours, occupants of distinct but neighbouring districts, as a
group having a different aspect from the Rhinoceros of Africa, though
some of these latter inhabit very similar countries, but others most
diverse stations. We find them intimately related [scarcely <?>
differences more than some breeds of cattle] in structure to the
Rhinoceros, which for immense periods have inhabited this one, out of
three main zoological divisions of the world. Yet some of these ancient
animals were fitted to very different stations: we find all three
<illegible> of the generic character of the Rhinoceros, which form a
[piece of net]1 set of links in the broken chain
representing the Pachydermata, as the chain likewise forms a portion in
other and longer chains. We see this wonderfully in dissecting the
coarse leg of all three and finding nearly the same bones as in bat's
wings or man's hand, but we see the clear mark in solid tibia of the
fusion into it of the fibula. In all three we find their heads composed
of three altered vertebræ, short neck, same bones as giraffe. In the
upper jaws of all three we find small teeth like rabbit's. In
dissecting them in fœtal state we find at a not very early stage their
form exactly alike the most different animals, and even with arteries
running as in a fish: and this similarity holds when the young one is
produced in womb, pond, egg or spawn. Now these three undoubted species
scarcely differ more than breeds of cattle,

1 The author doubtless meant
that the
complex relationships between organisms can be roughly represented by a
net in which the knots stand for species.

are probably subject to many the same contagious diseases;
if
domesticated these forms would vary, and they might possibly breed
together, and fuse into something1 different <from> their
aboriginal forms; might be selected to serve different ends.

Now the Creationist believes these three Rhinoceroses were
created2 with their deceptive appearance of true, not <illegible> relationship;
as well can I believe the planets revolve in their present courses not
from one law of gravity but from distinct volition of Creator.

If real species, sterile one with another, differently
adapted, now
inhabiting different countries, with different structures and
instincts, are admitted to have common descent, we can only
legitimately stop where our facts stop. Look how far in some case a
chain of species will lead us. <This probably refers to the Crustacea,
where the two ends of the series have "hardly a character in common." Origin,
Ed. i. p. 419.> May we not jump (considering how much extermination,
and how imperfect geological records) from one sub-genus to another
sub-genus. Can genera restrain us; many of the same arguments, which
made us give up species, inexorably demand genera and families and
orders to fall, and classes tottering. We ought to stop only when clear
unity of type, independent of use and adaptation, ceases.

Be it remembered no naturalist pretends to give test from
external
characters of species; in many genera the distinction is quite arbitrary3.
But there remains one other way of comparing species

1 Between the lines occurs:—"one
<?> form
be lost."

2 The original sentence is here
broken up
by the insertion of:—"out of the dust of Java, Sumatra, these <?>
allied to past and present age and <illegible>, with the stamp of
inutility in some of their organs and conversion in others."

3 Between the lines occur the
words:—"Species vary
according to same general laws as varieties; they cross according to
same laws."

with races; it is to compare the effects of crossing them.
Would it
not be wonderful, if the union of two organisms, produced by two
separate acts of Creation, blended their characters together when
crossed according to the same rules, as two races which have
undoubtedly descended from same parent stock; yet this can be shown to
be the case. For sterility, though a usual <?>, is not an invariable
concomitant, it varies much in degree and has been shown to be probably
dependent on causes closely analogous with those which make
domesticated organisms sterile. Independent of sterility there is no
difference between mongrels and hybrids, as can be shown in a long
series of facts. It is strikingly seen in cases of instincts, when the
minds of the two species or races become blended together1.
In both cases if the half-breed be crossed with either parent for a few
generations, all traces of the one parent form is lost (as Kölreuter in
two tobacco species almost sterile together), so that the Creationist
in the case of a species, must believe that one act of creation is
absorbed into another!

CONCLUSION.

Such are my reasons for believing that specific forms are
not
immutable. The affinity of different groups, the unity of types of
structure, the representative forms through which fœtus passes, the
metamorphosis of organs, the abortion of others cease to be
metaphorical expressions and become intelligible facts. We no longer
look <an> on animal as a savage does at a ship2, or other
great work of art, as a thing wholly beyond comprehension, but we

1 "A cross with a bull-dog has
affected
for many generations the courage and obstinacy of greyhounds," Origin,
Ed. i. p. 214, vi. p. 327.

2 The simile of the savage and
the ship
occurs in the Origin, Ed. i. p. 485, vi. p. 665.

feel far more interest in examining it. How interesting is
every
instinct, when we speculate on their origin as an hereditary or
congenital habit or produced by the selection of individuals differing
slightly from their parents. We must look at every complicated
mechanism and instinct, as the summary of a long history, <as the
summing up> of1 useful contrivances, much like a work of
art. How interesting does the distribution of all animals become, as
throwing light on ancient geography. [We see some seas bridged over.]
Geology loses in its glory from the imperfection of its archives2,
but how does it gain in the immensity of the periods of its formations
and of the gaps separating these formations. There is much grandeur in
looking at the existing animals either as the lineal descendants of the
forms buried under thousand feet of matter, or as the coheirs of some
still more ancient ancestor. It accords with what we know of the law
impressed on matter by the Creator, that the creation and extinction of
forms, like the birth and death of individuals should be the effect of
secondary [laws] means3. It is derogatory that the Creator
of countless systems of worlds should have created each of the myriads
of creeping parasites and [slimy] worms which have swarmed each day of
life on land and water <on> [this] one globe. We cease being
astonished, however much we may deplore, that a group of animals should
have been directly created to lay their eggs in bowels and flesh of
other,—that some organisms should delight in cruelty,—that animals
should be led away by false instincts,—that annually there should be an

1 In the Origin, Ed.
i. p. 486,
vi. p. 665, the author speaks of the "summing up of many contrivances":
I have therefore introduced the above words which make the passage
clearer. In the Origin the comparison is with "a great
mechanical invention,"—not
with a work of art.

incalculable waste of eggs and pollen. From death, famine,
rapine,
and the concealed war of nature we can see that the highest good, which
we can conceive, the creation of the higher animals has directly come.
Doubtless it at first transcends our humble powers, to conceive laws
capable of creating individual organisms, each characterised by the
most exquisite workmanship and widely-extended adaptations. It accords
better with [our modesty] the lowness of our faculties to suppose each
must require the fiat of a creator, but in the same proportion the
existence of such laws should exalt our notion of the power of the
omniscient Creator1. There is a simple grandeur in the view
of life with its powers of growth, assimilation and reproduction, being
originally breathed into matter under one or a few forms, and that
whilst this our planet has gone circling on according to fixed laws,
and land and water, in a cycle of change, have gone on replacing each
other, that from so simple an origin, through the process of gradual
selection of infinitesimal changes, endless forms most beautiful and
most wonderful have been evolved2.

1 The following discussion,
together with
some memoranda are on the last page of the MS. "The
supposed creative
spirit does not create either number or kind which <are> from analogy
adapted to site (viz. New Zealand): it does not keep them all
permanently adapted to any country,—it works on spots or areas of
creation,—it is not persistent for great periods,—it creates forms of
same groups in same regions, with no physical similarity,—it creates,
on islands or mountain summits, species allied to the neighbouring
ones, and not allied to alpine nature as shown in other mountain
summits—even different on
different island of similarly constituted
archipelago, not created on two points: never mammifers created on
small isolated island; nor number of organisms adapted to locality: its
power seems influenced or related to the range of other species wholly
distinct of the same genus,—it does not equally effect, in amount of
difference, all the groups of the same class."

2 This passage is the ancestor
of the
concluding words in the first edition of the Origin of Species which
have remained substantially unchanged throughout subsequent editions,
"There is grandeur in this view of life, with its several powers,
having been originally breathed into a few forms or into one; and that
whilst this planet has gone cycling on according to the fixed law of
gravity, from so simple a beginning endless forms most

N.B.—There ought somewhere to be a discussion from Lyell
to show
that external conditions do vary, or a note to Lyell's works <work?>.

Besides other difficulties in ii. Part,
non-acclimatisation of
plants. Difficulty when asked how did white and negro become
altered from common intermediate stock: no facts. We do NOT know that
species are immutable, on the contrary. What arguments against this
theory, except our not perceiving every step, like the erosion of
valleys1.

beautiful and most wonderful have been, and are being,
evolved." In
the 2nd edition "by the Creator" is introduced after "originally
breathed."

1 Compare the Origin, Ed.
i. p.
481, vi. p. 659, "The difficulty is the same as that felt by so many
geologists, when Lyell first insisted that long lines of inland cliffs
had been formed, and great valleys excavated, by the slow action of the
coast-waves."

ON THE VARIATION OF ORGANIC BEINGS UNDER
DOMESTICATION; AND ON THE PRINCIPLES OF SELECTION

THE most favourable conditions for variation seem to be
when organic
beings are bred for many generations under domestication1:
one may infer this from the simple fact of the vast number of races and
breeds of almost every plant and animal, which has long been
domesticated. Under certain conditions organic beings even during their
individual lives become slightly altered from their usual form, size,
or other characters: and many of the peculiarities thus acquired are
transmitted to their offspring. Thus in animals, the size and vigour of
body, fatness, period of maturity, habits of body or consensual
movements, habits of mind and temper, are modified or acquired during
the life of the individual2, and become inherited. There is
reason to believe that when long exercise has given to certain muscles
great development, or disuse has lessened them, that such development
is also in-

1 The cumulative effect of
domestication
is insisted on in the Origin, see e.g. Origin, Ed.
i. p. 7, vi. p. 8.

2 This type of variation passes
into what
he describes as the direct effect of conditions. Since they are due to
causes acting during the adult life of the organism they might be
called individual variations, but he uses this term for congenital
variations, e.g. the differences discoverable in plants
raised from seeds of the same pod (Origin, Ed. i. p. 45, vi.
p. 53).

herited. Food and climate will occasionally produce
changes in the
colour and texture of the external coverings of animals; and certain
unknown conditions affect the horns of cattle in parts of Abyssinia;
but whether these peculiarities, thus acquired during individual lives,
have been inherited, I do not know. It appears certain that
malconformation and lameness in horses, produced by too much work on
hard roads,—that affections of the eyes in this animal probably caused
by bad ventilation,—that tendencies towards many diseases in man, such
as gout, caused by the course of life and ultimately producing changes
of structure, and that many other diseases produced by unknown
agencies, such as goitre, and the idiotcy resulting from it, all become
hereditary.

It is very doubtful whether the flowers and leaf-buds,
annually
produced from the same bulb, root, or tree, can properly be considered
as parts of the same individual, though in some respects they certainly
seem to be so. If they are parts of an individual, plants also are
subject to considerable changes during their individual lives.
Most florist-flowers if neglected degenerate, that is, they lose some
of their characters; so common is this, that trueness is often stated,
as greatly enhancing the value of a variety1: tulips break
their colours only after some years' culture; some plants become double
and others single, by neglect or care: these characters can be
transmitted by cuttings or grafts, and in some cases by true or seminal
propagation. Occasionally a single bud on a plant assumes at once a new
and widely different character: thus it is certain that nectarines have
been produced on

1 <It is not clear where the
following
note is meant to come>: Case of Orchis,—most remarkable as not long
cultivated by seminal propagation. Case of varieties which soon
acquire, like Ægilops and Carrot (and Maize) a certain
general character and then go on varying.

peach trees and moss roses on provence roses; white
currants on red
currant bushes; flowers of a different colour from that of the stock,
in Chrysanthemums, Dahlias, sweet-williams, Azaleas, &c., &c.;
variegated leaf-buds on many trees, and other similar cases. These new
characters appearing in single buds, can, like those lesser changes
affecting the whole plant, be multiplied not only by cuttings and such
means, but often likewise by true seminal generation.

The changes thus appearing during the lives of individual
animals
and plants are extremely rare compared with those which are congenital
or which appear soon after birth. Slight differences thus arising are
infinitely numerous: the proportions and form of every part of the
frame, inside and outside, appear to vary in very slight degrees:
anatomists dispute what is the "beau ideal" of the bones, the liver and
kidneys, like painters do of the proportions of the face: the
proverbial expression that no two animals or plants are born absolutely
alike, is much truer when applied to those under domestication, than to
those in a state of nature1. Besides these slight
differences, single individuals are occasionally born considerably
unlike in certain parts or in their whole structure to their parents:
these are called by horticulturalists and breeders "sports"; and are
not uncommon except when very strongly marked. Such sports are known in
some cases to have been parents of some of our domestic races; and such
probably have been the parents of many other races, especially of those
which in some senses may be called hereditary monsters; for instance
where there is an additional limb, or where all the limbs are stunted
(as in the Ancon sheep), or where a part is wanting, as in rumpless
fowls and tailless

1Here, as in the MS.
of 1842,
the author is inclined to minimise the variation occurring in nature.

dogs or cats1. The effects of external
conditions on the
size, colour and form, which can rarely and obscurely be detected
during one individual life, become apparent after several generations:
the slight differences, often hardly describable, which characterize
the stock of different countries, and even of districts in the same
country, seem to be due to such continued action.

On the hereditary tendency.

A volume might be filled with facts showing what a strong
tendency
there is to inheritance, in almost every case of the most trifling, as
well as of the most remarkable congenital peculiarities2.
The term congenital peculiarity, I may remark, is a loose expression
and can only mean a peculiarity apparent when the part affected is
nearly or fully developed: in the Second Part, I shall have to discuss
at what period of the embryonic life connatal peculiarities probably
first appear; and I shall then be able to show from some evidence, that
at whatever period of life a new peculiarity first appears, it tends
hereditarily to appear at a corresponding period3. Numerous
though slight changes, slowly supervening in animals during mature life
(often, though by no means always, taking the form of disease), are, as
stated in the first paragraphs, very often hereditary. In plants,
again, the buds which assume a different character from their stock
likewise tend to transmit their new peculiarities. There is not
sufficient reason to believe that either mutilations4 or
changes of form produced by

1 This is more strongly stated
than in the Origin, Ed. i. p. 30.

2See Origin,
Ed. i.
p. 13.

3Origin, Ed. i. p.
86, vi. p.
105.

4 It is interesting to find that
though
the author, like his contemporaries, believed in the inheritance of
acquired characters, he excluded the case of mutilation.

mechanical pressure, even if continued for hundreds of
generations,
or that any changes of structure quickly produced by disease, are
inherited; it would appear as if the tissue of the part affected must
slowly and freely grow into the new form, in order to be inheritable.
There is a very great difference in the hereditary tendency of
different peculiarities, and of the same peculiarity, in different
individuals and species; thus twenty thousand seeds of the weeping ash
have been sown and not one come up true;—out of seventeen seeds of the
weeping yew, nearly all came up true. The ill-formed and almost
monstrous "Niata" cattle of S. America and Ancon sheep, both when bred
together and when crossed with other breeds, seem to transmit their
peculiarities to their offspring as truly as the ordinary breeds. I can
throw no light on these differences in the power of hereditary
transmission. Breeders believe, and apparently with good cause, that a
peculiarity generally becomes more firmly implanted after having passed
through several generations; that is if one offspring out of twenty
inherits a peculiarity from its parents, then its descendants will tend
to transmit this peculiarity to a larger proportion than one in twenty;
and so on in succeeding generations. I have said nothing about mental
peculiarities being inheritable for I reserve this subject for a
separate chapter.

Causes of Variation.

Attention must here be drawn to an important distinction
in the
first origin or appearance of varieties: when we see an animal highly
kept producing offspring with an hereditary tendency to early maturity
and fatness; when we see the wild-duck and Australian dog always
becoming, when bred for one or a few generations in confinement,

mottled in their colours; when we see people living in
certain
districts or circumstances becoming subject to an hereditary taint to
certain organic diseases, as consumption or plica polonica,—we
naturally attribute such changes to the direct effect of known or
unknown agencies acting for one or more generations on the parents. It
is probable that a multitude of peculiarities may be thus directly
caused by unknown external agencies. But in breeds, characterized by an
extra limb or claw, as in certain fowls and dogs; by an extra joint in
the vertebræ; by the loss of a part, as the tail; by the substitution
of a tuft of feathers for a comb in certain poultry; and in a multitude
of other cases, we can hardly attribute these peculiarities directly to
external influences, but indirectly to the laws of embryonic growth and
of reproduction. When we see a multitude of varieties (as has often
been the case, where a cross has been carefully guarded against)
produced from seeds matured in the very same capsule1, with
the male and female principle nourished from the same roots and
necessarily exposed to the same external influences; we cannot believe
that the endless slight differences between seedling varieties thus
produced, can be the effect of any corresponding difference in their
exposure. We are led (as Müller has remarked) to the same conclusion,
when we see in the same litter, produced by the same act of conception,
animals considerably different.

As variation to the degree here alluded to has been
observed only in
organic beings under domestication, and in plants amongst those most
highly and long cultivated, we must attribute, in such cases, the
varieties (although the difference between each variety cannot possibly
be attributed to any corresponding difference of exposure in the
parents) to the indirect effects of domestication on the action of

the reproductive system1. It would appear as if
the
reproductive powers failed in their ordinary function of producing new
organic beings closely like their parents; and as if the entire
organization of the embryo, under domestication, became in a slight
degree plastic2. We shall hereafter have occasion to show,
that in organic beings, a considerable change from the natural
conditions of life, affects, independently of their general state of
health, in another and remarkable manner the reproductive system. I may
add, judging from the vast number of new varieties of plants which have
been produced in the same districts and under nearly the same routine
of culture, that probably the indirect effects of domestication in
making the organization plastic, is a much more efficient source of
variation than any direct effect which external causes may have on the
colour, texture, or form of each part. In the few instances in which,
as in the Dahlia3, the course of variation has been
recorded, it appears that domestication produces little effect for
several generations in rendering the organization plastic; but
afterwards, as if by an accumulated effect, the original character of
the species suddenly gives way or breaks.

On Selection.

We have hitherto only referred to the first appearance in
individuals of new peculiarities; but to make a race or breed,
something more is generally4 requisite than such
peculiarities (except

1Origin, Ed. i. p. 8,
vi. p. 10.

2For plasticity see Origin,
Ed. i. pp. 12, 132.

3Var. under Dom., Ed.
ii. i. p.
393.

4 Selection is here used in the
sense of
isolation, rather than as implying the summation of small differences.
Professor Henslow in his Heredity of Acquired Characters in Plants,
1908, p. 2, quotes from Darwin's Var. under Dom., Ed. i. II.
p. 271, a passage in which the author, speaking of the direct action of
conditions, says:—"A new sub-variety would thus be produced without
the aid of selection." Darwin certainly

in the case of the peculiarities being the direct effect
of
constantly surrounding conditions) should be inheritable,—namely the
principle of selection, implying separation. Even in the rare instances
of sports, with the hereditary tendency very strongly implanted,
crossing must be prevented with other breeds, or if not prevented the
best characterized of the half-bred offspring must be carefully
selected. Where the external conditions are constantly tending to give
some character, a race possessing this character will be formed with
far greater ease by selecting and breeding together the individuals
most affected. In the case of the endless slight variations produced by
the indirect effects of domestication on the action of the reproductive
system, selection is indispensable to form races; and when carefully
applied, wonderfully numerous and diverse races can be formed.
Selection, though so simple in theory, is and has been important to a
degree which can hardly be overrated. It requires extreme skill, the
results of long practice, in detecting the slightest difference in the
forms of animals, and it implies some distinct object in view; with
these requisites and patience, the breeder has simply to watch for
every the smallest approach to the desired end, to select such
individuals and pair them with the most suitable forms, and so continue
with succeeding generations. In most cases careful selection and the
prevention of accidental crosses will be necessary for several
generations, for in new breeds there is a strong tendency to vary and
especially to revert to ancestral forms: but in every succeeding
generation less care will be requisite for the breed will become

did not mean to imply that such varieties
are freed
from the action of natural selection, but merely that a new form may
appear without summation of new characters. Professor
Henslow is apparently unaware that the above passage is omitted in the
second edition of Var. under Dom., II. p. 260.

truer; until ultimately only an occasional individual will
require
to be separated or destroyed. Horticulturalists in raising seeds
regularly practise this, and call it "roguing," or destroying the
"rogues" or false varieties. There is another and less efficient means
of selection amongst animals: namely repeatedly procuring males with
some desirable qualities, and allowing them and their offspring to
breed freely together; and this in the course of time will affect the
whole lot. These principles of selection have been methodically followed
for scarcely a century; but their high importance is shown by the
practical results, and is admitted in the writings of the most
celebrated agriculturalists and horticulturalists;—I need only name
Anderson, Marshall, Bakewell, Coke, Western, Sebright and Knight.

Even in well-established breeds the individuals of which
to an
unpractised eye would appear absolutely similar, which would give, it
might have been thought, no scope to selection, the whole appearance of
the animal has been changed in a few years (as in the case of Lord
Western's sheep), so that practised agriculturalists could scarcely
credit that a change had not been effected by a cross with other
breeds. Breeders both of plants and animals frequently give their means
of selection greater scope, by crossing different breeds and selecting
the offspring; but we shall have to recur to this subject again.

The external conditions will doubtless influence and
modify the
results of the most careful selection; it has been found impossible to
prevent certain breeds of cattle from degenerating on mountain
pastures; it would probably be impossible to keep the plumage of the
wild-duck in the domesticated race; in certain soils, no care has been
sufficient to raise cauliflower seed true to its character; and so

in many other cases. But with patience it is wonderful
what man has
effected. He has selected and therefore in one sense made one breed of
horses to race and another to pull; he has made sheep with fleeces good
for carpets and other sheep good for broadcloth; he has, in the same
sense, made one dog to find game and give him notice when found, and
another dog to fetch him the game when killed; he has made by selection
the fat to lie mixed with the meat in one breed and in another to
accumulate in the bowels for the tallow-chandler1; he has
made the legs of one breed of pigeons long, and the beak of another so
short, that it can hardly feed itself; he has previously determined how
the feathers on a bird's body shall be coloured, and how the petals of
many flowers shall be streaked or fringed, and has given prizes for
complete success;—by selection, he has made the leaves of one variety
and the flower-buds of another variety of the cabbage good to eat, at
different seasons of the year; and thus has he acted on endless
varieties. I do not wish to affirm that the long- and short-wooled
sheep, or that the pointer and retriever, or that the cabbage and
cauliflower have certainly descended from one and the same aboriginal
wild stock; if they have not so descended, though it lessens what man
has effected, a large result must be left unquestioned.

In saying as I have done that man makes a breed, let it
not be
confounded with saying that man makes the individuals, which are given
by nature with certain desirable qualities; man only adds together and
makes a permanent gift of nature's bounties. In several cases, indeed,
for instance in the "Ancon" sheep, valuable from not getting over
fences, and in the turnspit dog, man has probably only prevented
crossing; but in many cases we positively

know that he has gone on selecting, and taking advantage
of
successive small variations.

Selection1 has been methodically followed,
as
I have said, for barely a century; but it cannot be doubted that
occasionally it has been practised from the remotest ages, in those
animals completely under the dominion of man. In the earliest chapters
of the Bible there are rules given for influencing the colours of
breeds, and black and white sheep are spoken of as separated. In the
time of Pliny the barbarians of Europe and Asia endeavoured by
cross-breeding with a wild stock to improve the races of their dogs and
horses. The savages of Guyana now do so with their dogs: such care
shows at least that the characters of individual animals were attended
to. In the rudest times of English history, there were laws to prevent
the exportation of fine animals of established breeds, and in the case
of horses, in Henry VIII's time, laws for the destruction of all horses
under a certain size. In one of the oldest numbers of the Phil.
Transactions, there are rules for selecting and improving the
breeds of sheep. Sir H. Bunbury, in 1660, has given rules for selecting
the finest seedling plants, with as much precision as the best recent
horticulturalist could. Even in the most savage and rude nations, in
the wars and famines which so frequently occur, the most useful of
their animals would be preserved: the value set upon animals by savages
is shown by the inhabitants of Tierra del Fuego devouring their old
women before their dogs, which as they asserted are useful in
otter-hunting2: who can doubt but that in every case of
famine and war, the best otter-hunters would be preserved, and
therefore in fact selected for breeding. As the offspring so obviously

1 See Origin, Ed. i.
p. 33, vi.
p. 38. The evidence is given in the present Essay rather more fully
than in the Origin.

take after their parents, and as we have seen that savages
take
pains in crossing their dogs and horses with wild stocks, we may even
conclude as probable that they would sometimes pair the most useful of
their animals and keep their offspring separate. As different races of
men require and admire different qualities in their domesticated
animals, each would thus slowly, though unconsciously, be selecting a
different breed. As Pallas has remarked, who can doubt but that the
ancient Russian would esteem and endeavour to preserve those sheep in
his flocks which had the thickest coats. This kind of insensible
selection by which new breeds are not selected and kept separate, but a
peculiar character is slowly given to the whole mass of the breed, by
often saving the life of animals with certain characteristics, we may
feel nearly sure, from what we see has been done by the more direct
method of separate selection within the last 50 years in England, would
in the course of some thousand years produce a marked effect.

Crossing Breeds.

When once two or more races are formed, or if more than
one race, or
species fertile inter se, originally existed in a wild state,
their crossing becomes a most copious source of new races1.
When two well-marked races are crossed the offspring in the first
generation take more or less after either parent or are quite
intermediate between them, or rarely assume characters in some degree
new. In the second and several succeeding generations, the offspring
are generally found to

1 The effects of crossing is
much more
strongly stated here than in the Origin. See Ed. i. p. 20,
vi. p. 23, where indeed the opposite point of view is given. His change
of opinion may be due to his work on pigeons. The whole of the
discussion on crossing corresponds to Chapter VIII of the Origin,
Ed. i. rather than to anything in the earlier part of the book.

vary exceedingly, one compared with another, and many
revert nearly
to their ancestral forms. This greater variability in succeeding
generations seems analogous to the breaking or variability of organic
beings after having been bred for some generations under domestication1.
So marked is this variability in cross-bred descendants, that
Pallas and some other naturalists have supposed that all variation is
due to an original cross; but I conceive that the history of the
potato, Dahlia, Scotch Rose, the guinea-pig, and of many trees in this
country, where only one species of the genus exists, clearly shows that
a species may vary where there can have been no crossing. Owing to this
variability and tendency to reversion in cross-bred beings, much
careful selection is requisite to make intermediate or new permanent
races: nevertheless crossing has been a most powerful engine,
especially with plants, where means of propagation exist by which the
cross-bred varieties can be secured without incurring the risk of fresh
variation from seminal propagation: with animals the most skilful
agriculturalists now greatly prefer careful selection from a
well-established breed, rather than from uncertain cross-bred stocks.

Although intermediate and new races may be formed by the
mingling of
others, yet if the two races are allowed to mingle quite freely, so
that none of either parent race remain pure, then, especially if the
parent races are not widely different, they will slowly blend together,
and the two races will be destroyed, and one mongrel race left in its
place. This will of course happen in a shorter time, if one

1 The parallelism between the
effects of a
cross and the effects of conditions is given from a different point of
view in the Origin, Ed. i. p. 266, vi. p. 391. See the
experimental evidence for this important principle in the author's work
on Cross and Self-Fertilisation. Professor Bateson has
suggested that the experiments should be repeated with gametically pure
plants.

of the parent races exists in greater number than the
other. We see
the effect of this mingling, in the manner in which the aboriginal
breeds of dogs and pigs in the Oceanic Islands and the many breeds of
our domestic animals introduced into S. America, have all been lost and
absorbed in a mongrel race. It is probably owing to the freedom of
crossing, that, in uncivilised countries, where inclosures do not
exist, we seldom meet with more than one race of a species: it is only
in enclosed countries, where the inhabitants do not migrate, and have
conveniences for separating the several kinds of domestic animals, that
we meet with a multitude of races. Even in civilised countries, want of
care for a few years has been found to destroy the good results of far
longer periods of selection and separation.

This power of crossing will affect the races of all terrestrial animals; for all terrestrial animals require for their
reproduction the union of two individuals. Amongst plants, races will
not cross and blend together with so much freedom as in terrestrial
animals; but this crossing takes place through various curious
contrivances to a surprising extent. In fact such contrivances exist in
so very many hermaphrodite flowers by which an occasional cross may
take place, that I cannot avoid suspecting (with Mr Knight) that the
reproductive action requires, at intervals, the concurrence
of distinct individuals1. Most breeders of plants
and animals are firmly convinced that benefit is derived from an
occasional cross, not with another race, but with another family of the
same race; and that, on the other hand, injurious consequences follow
from long-continued close interbreeding in the same

1 The so-called Knight-Darwin
Law is often
misunderstood. See Goebel in Darwin and Modern Science, 1909,
p. 419; also F. Darwin, Nature, Oct. 27, 1898.

family. Of marine animals, many more, than was till lately
believed,
have their sexes on separate individuals; and where they are
hermaphrodite, there seems very generally to be means through the water
of one individual occasionally impregnating another: if individual
animals can singly propagate themselves for perpetuity, it is
unaccountable that no terrestrial animal, where the means of
observation are more obvious, should be in this predicament of singly
perpetuating its kind. I conclude, then, that races of most animals and
plants, when unconfined in the same country, would tend to blend
together.

Whether our domestic races have
descended from
one or more wild stocks.

Several naturalists, of whom Pallas1 regarding
animals,
and Humboldt regarding certain plants, were the first, believe that the
breeds of many of our domestic animals such as of the horse, pig, dog,
sheep, pigeon, and poultry, and of our plants have descended from more
than one aboriginal form. They leave it doubtful, whether such forms
are to be considered wild races, or true species, whose offspring are
fertile when crossed inter se. The main arguments for this
view consist, firstly, of the great difference between such breeds, as
the Race- and Cart-Horse, or the Greyhound and Bull-dog, and of our
ignorance of the steps or stages through which these could have passed
from a common parent; and secondly that in the most ancient historical
periods, breeds resembling some of those at present most different,
existed in different countries. The wolves of N. America and of Siberia
are thought to be different species; and

it has been remarked that the dogs belonging to the
savages in these
two countries resemble the wolves of the same country; and therefore
that they have probably descended from two different wild stocks. In
the same manner, these naturalists believe that the horse of Arabia and
of Europe have probably descended from two wild stocks both apparently
now extinct. I do not think the assumed fertility of these wild stocks
any very great difficulty on this view; for although in animals the
offspring of most cross-bred species are infertile, it is not always
remembered that the experiment is very seldom fairly tried, except when
two near species both breed freely (which does not readily
happen, as we shall hereafter see) when under the dominion of man.
Moreover in the case of the China1 and common goose, the
canary and siskin, the hybrids breed freely; in other cases the
offspring from hybrids crossed with either pure parent are fertile, as
is practically taken advantage of with the yak and cow; as far as the
analogy of plants serves, it is impossible to deny that some species
are quite fertile inter se; but to this subject we shall
recur.

On the other hand, the upholders of the view that the
several breeds
of dogs, horses, &c., &c., have descended each from one stock,
may aver that their view removes all difficulty about fertility,
and that the main argument from the high antiquity of different breeds,
somewhat similar to the present breeds, is worth little without knowing
the date of the domestication of such animals, which is far from being
the case. They may also with more weight aver that, knowing that
organic beings under domestication do vary in some degree, the argument
from the great difference between certain breeds is

1 See Darwin's paper on the
fertility of
hybrids from the common and Chinese goose in Nature, Jan. 1,
1880.

worth nothing, without we know the limits of variation
during a long
course of time, which is far from the case. They may argue that almost
every county in England, and in many districts of other countries, for
instance in India, there are slightly different breeds of the domestic
animals; and that it is opposed to all that we know of the distribution
of wild animals to suppose that these have descended from so many
different wild races or species: if so, they may argue, is it not
probable that countries quite separate and exposed to different
climates would have breeds not slightly, but considerably, different?
Taking the most favourable case, on both sides, namely that of the dog;
they might urge that such breeds as the bull-dog and turnspit have been
reared by man, from the ascertained fact that strictly analogous breeds
(namely the Niata ox and Ancon sheep) in other quadrupeds have thus
originated. Again they may say, seeing what training and careful
selection has effected for the greyhound, and seeing how absolutely
unfit the Italian greyhound is to maintain itself in a state of nature,
is it not probable that at least all greyhounds,—from the rough
deerhound, the smooth Persian, the common English, to the Italian,—have
descended from one stock1? If so, is it so improbable that
the deer-hound and long-legged shepherd dog have so descended? If we
admit this, and give up the bulldog, we can hardly dispute the probable
common descent of the other breeds.

The evidence is so conjectural and balanced on both sides
that at
present I conceive that no one can decide: for my own part, I lean to
the probability of most of our domestic animals having descended from
more than one wild stock; though from the arguments last advanced and
from reflecting on the slow though inevitable effect of

different races of mankind, under different circumstances,
saving
the lives of and therefore selecting the individuals most useful to
them, I cannot doubt but that one class of naturalists have much
overrated the probable number of the aboriginal wild stocks. As far as
we admit the difference of our races <to be> due to the differences of
their original stocks, so much must we give up of the amount of
variation produced under domestication. But this appears to me
unimportant, for we certainly know in some few cases, for instance in
the Dahlia, and potato, and rabbit, that a great number of varieties
have proceeded from one stock; and, in many of our domestic races, we
know that man, by slowly selecting and by taking advantage of sudden
sports, has considerably modified old races and produced new ones.
Whether we consider our races as the descendants of one or several wild
stocks, we are in far the greater number of cases equally ignorant what
these stocks were.

Limits to Variation in degree and kind.

Man's power in making races depends, in the first
instance, on the
stock on which he works being variable; but his labours are modified
and limited, as we have seen, by the direct effects of the external
conditions,—by the deficient or imperfect hereditariness of new
peculiarities,—and by the tendency to continual variation and
especially to reversion to ancestral forms. If the stock is not
variable under domestication, of course he can do nothing; and it
appears that species differ considerably in this tendency to variation,
in the same way as even sub-varieties from the same variety differ
greatly in this respect, and transmit to their offspring this
difference in tendency. Whether the absence of a tendency to vary is an
unalterable quality in certain

species, or depends on some deficient condition of the
particular
state of domestication to which they are exposed, there is no evidence.
When the organization is rendered variable, or plastic, as I have
expressed it, under domestication, different parts of the frame vary
more or less in different species: thus in the breeds of cattle it has
been remarked that the horns are the most constant or least variable
character, for these often remain constant, whilst the colour, size,
proportions of the body, tendency to fatten &c., vary; in sheep, I
believe, the horns are much more variable. As a general rule the less
important parts of the organization seem to vary most, but I think
there is sufficient evidence that every part occasionally varies in a
slight degree. Even when man has the primary requisite variability he
is necessarily checked by the health and life of the stock he is
working on: thus he has already made pigeons with such small beaks that
they can hardly eat and will not rear their own young; he has made
families of sheep with so strong a tendency to early maturity and to
fatten, that in certain pastures they cannot live from their extreme
liability to inflammation; he has made (i.e. selected)
sub-varieties of plants with a tendency to such early growth that they
are frequently killed by the spring frosts; he has made a breed of cows
having calves with such large hinder quarters that they are born with
great difficulty, often to the death of their mothers1; the
breeders were compelled to remedy this by the selection of a breeding
stock with smaller hinder quarters; in such a case, however, it is
possible by long patience and great loss, a remedy might have been
found in selecting cows capable of giving birth to calves with large
hinder quarters, for in human kind there <are> no doubt hereditary bad
and

good confinements. Besides the limits already specified,
there can
be little doubt that the variation of different parts of the frame are
connected together by many laws1: thus the two sides of the
body, in health and disease, seem almost always to vary together: it
has been asserted by breeders that if the head is much elongated, the
bones of the extremities will likewise be so; in seedling-apples large
leaves and fruit generally go together, and serve the horticulturalist
as some guide in his selection; we can here see the reason, as the
fruit is only a metamorphosed leaf. In animals the teeth and hair seem
connected, for the hairless Chinese dog is almost toothless. Breeders
believe that one part of the frame or function being increased causes
other parts to decrease: they dislike great horns and great bones as so
much flesh lost; in hornless breeds of cattle certain bones of the head
become more developed: it is said that fat accumulating in one part
checks its accumulation in another, and likewise checks the action of
the udder. The whole organization is so connected that it is probable
there are many conditions determining the variation of each part, and
causing other parts to vary with it; and man in making new races must
be limited and ruled by all such laws.

In what consists Domestication.

In this chapter we have treated of variation under
domestication,
and it now remains to consider in what does this power of domestication
consist2, a subject of considerable difficulty. Observing
that organic beings of almost every class, in all climates, countries,
and times, have varied when long bred

under domestication, we must conclude that the influence
is of some
very general nature1. Mr Knight alone, as far as I know, has
tried to define it; he believes it consists of an excess of food,
together with transport to a more genial climate, or protection from
its severities. I think we cannot admit this latter proposition, for we
know how many vegetable products, aborigines of this country, here
vary, when cultivated without any protection from the weather; and some
of our variable trees, as apricots, peaches, have undoubtedly been
derived from a more genial climate. There appears to be much more truth
in the doctrine of excess of food being the cause, though I much doubt
whether this is the sole cause, although it may well be requisite for
the kind of variation desired by man, namely increase of size and
vigour. No doubt horticulturalists, when they wish to raise new
seedlings, often pluck off all the flower-buds, except a few, or remove
the whole during one season, so that a great stock of nutriment may be
thrown into the flowers which are to seed. When plants are transported
from high-lands, forests, marshes, heaths, into our gardens and
greenhouses, there must be a considerable change of food, but it would
be hard to prove that there was in every case an excess of the kind
proper to the plant. If it be an excess of food, compared with that
which the being obtained in its natural state2, the effects
continue for an improbably long time; during how many ages has

2 <Note in the original.> "It
appears that
slight changes of condition <are> good for health; that more change
affects the generative system, so that variation results in the
offspring; that still more change checks or destroys fertility not of
the offspring." Compare the Origin, Ed. i. p. 9, vi. p. 11.
What the meaning of "not of the offspring" may be is not clear.

wheat been cultivated, and cattle and sheep reclaimed, and
we cannot
suppose their amount of food has gone on increasing,
nevertheless these are amongst the most variable of our domestic
productions. It has been remarked (Marshall) that some of the most
highly kept breeds of sheep and cattle are truer or less variable than
the straggling animals of the poor, which subsist on commons, and pick
up a bare subsistence1. In the case of forest-trees raised
in nurseries, which vary more than the same trees do in their
aboriginal forests, the cause would seem simply to lie in their not
having to struggle against other trees and weeds, which in their
natural state doubtless would limit the conditions of their existence.
It appears to me that the power of domestication resolves itself into
the accumulated effects of a change of all or some of the natural
conditions of the life of the species, often associated with excess of
food. These conditions moreover, I may add, can seldom remain, owing to
the mutability of the affairs, habits, migrations, and knowledge of
man, for very long periods the same. I am the more inclined to come to
this conclusion from finding, as we shall hereafter show, that changes
of the natural conditions of existence seem peculiarly to affect the
action of the reproductive system2. As we see that hybrids
and mongrels, after the first generation, are apt to vary much, we may
at least conclude that variability does not altogether depend on excess
of food.

After these views, it may be asked how it comes

1 In the Origin, Ed.
i. p. 41,
vi. p. 46 the question is differently treated; it is pointed out that a
large stock of individuals gives a better chance of available
variations occurring. Darwin quotes from Marshall that sheep in small
lots can never be improved. This comes from Marshall's Review of
the Reports to the Board of Agriculture, 1808, p. 406. In this
Essay the name Marshall occurs in the margin. Probably this refers to loc.
cit. p. 200, where unshepherded sheep in many parts of England
are said to be similar owing to mixed breeding not being avoided.

that certain animals and plants, which have been
domesticated for a
considerable length of time, and transported from very different
conditions of existence, have not varied much, or scarcely at all; for
instance, the ass, peacock, guinea-fowl, asparagus, Jerusalem artichoke1.
I have already said that probably different species, like different
sub-varieties, possess different degrees of tendency to vary; but I am
inclined to attribute in these cases the want of numerous races less to
want of variability than to selection not having been practised on
them. No one will take the pains to select without some corresponding
object, either of use or amusement; the individuals raised must be
tolerably numerous, and not so precious, but that he may freely destroy
those not answering to his wishes. If guinea-fowls or peacocks2 became "fancy" birds, I cannot doubt that after some generations
several breeds would be raised. Asses have not been worked on from mere
neglect; but they differ in some degree in different
countries. The insensible selection, due to different races of mankind
preserving those individuals most useful to them in their different
circumstances, will apply only to the oldest and most widely
domesticated animals. In the case of plants, we must put entirely out
of the case those exclusively (or almost so) propagated by cuttings,
layers or tubers, such as the Jerusalem artichoke and laurel; and if we
put on one side plants of little ornament or use, and those which are
used at so early a period of their growth that no especial characters
signify, as asparagus3 and seakale, I can think of none long
cultivated which have not varied. In no case ought we to expect to find
as much variation in a race when it alone has been formed, as when
several have been formed,

for their crossing and recrossing will greatly increase
their
variability.

Summary of first Chapter.

To sum up this chapter. Races are made under
domestication: 1st, by
the direct effects of the external conditions to which the species is
exposed: 2nd, by the indirect effects of the exposure to new
conditions, often aided by excess of food, rendering the organization
plastic, and by man's selecting and separately breeding certain
individuals, or introducing to his stock selected males, or often
preserving with care the life of the individuals best adapted to his
purposes: 3rd, by crossing and recrossing races already made, and
selecting their offspring. After some generations man may relax his
care in selection: for the tendency to vary and to revert to ancestral
forms will decrease, so that he will have only occasionally to remove
or destroy one of the yearly offspring which departs from its type.
Ultimately, with a large stock, the effects of free crossing would
keep, even without this care, his breed true. By these means man can
produce infinitely numerous races, curiously adapted to ends, both most
important and most frivolous; at the same time that the effects of the
surrounding conditions, the laws of inheritance, of growth, and of
variation, will modify and limit his labours.

ON THE VARIATION OF ORGANIC BEINGS IN A
WILD STATE; ON THE NATURAL MEANS OF SELECTION; AND ON THE COMPARISON OF
DOMESTIC RACES AND TRUE SPECIES

HAVING treated of variation under domestication, we now
come to it in a state of nature.

Most organic beings in a state of nature vary exceedingly
little1: I put out of the case variations (as stunted plants
&c., and sea-shells in brackish water2) which are
directly the effect of external agencies and which we do not know
are in the breed3, or are hereditary. The
amount of hereditary variation is very difficult to ascertain, because
naturalists (partly from the want of knowledge, and partly from the
inherent difficulty of the subject) do not all agree whether certain
forms are species or races4. Some strongly marked races of
plants, comparable with the decided sports of horti-

1 In Chapter II of the first
edition of the Origin Darwin insists rather on the presence
of variability in a state of nature; see for instance, p. 45, Ed. vi.
p. 53, "I am convinced that the most experienced naturalist would be
surprised at the number of the cases of variability...which he could
collect on good authority, as I have collected, during a course of
years."

2 See Origin, Ed. i.
p. 44, vi. p. 52.

3 <Note in the original.> Here
discuss what is a species, sterility can most rarely be told
when crossed.—Descent from common stock.

4 <Note in the original.> Give
only rule: chain of intermediate forms, and analogy; this
important. Every Naturalist at first when he gets hold of new variable
type is quite puzzled to know what to think species and what
variations.

culturalists, undoubtedly exist in a state of nature, as
is actually known by experiment, for instance in the primrose and
cowslip1, in two so-called species of dandelion,
in two of foxglove2, and I believe in some pines. Lamarck
has observed that, as long as we confine our attention to one limited
country, there is seldom much difficulty in deciding what forms to call
species and what varieties; and that it is when collections flow in
from all parts of the world that naturalists often feel at a loss to
decide the limit of variation. Undoubtedly so it is, yet amongst
British plants (and I may add land shells), which are probably better
known than any in the world, the best naturalists differ very greatly
in the relative proportions of what they call species and what
varieties. In many genera of insects, and shells, and plants, it seems
almost hopeless to establish which are which. In the higher classes
there are less doubts; though we find considerable difficulty in
ascertaining what deserve to be called species amongst foxes and
wolves, and in some birds, for instance in the case of the white
barn-owl. When specimens are brought from different parts of the world,
how often do naturalists dispute this same question, as I found with
respect to the birds brought from the Galapagos islands. Yarrell has
remarked that the individuals of the same undoubted species of birds,
from Europe and N. America, usually present slight, indefinable though
perceptible differences. The recognition indeed of

1 The author had not at this
time the knowledge of the meaning of dimorphism.

2 <Note in original.> Compare
feathered heads in very different birds with spines in Echidna and
Hedgehog. <In Variation under Domestication, Ed. ii. vol. II.
p. 317, Darwin calls attention to laced and frizzled breeds occurring
in both fowls and pigeons. In the same way a peculiar form of covering
occurs in Echidna and the hedgehog.>

Plants under very different climate not
varying. Digitalis shows jumps <?> in variation, like Laburnum and
Orchis case—in fact hostile
cases. Variability of sexual characters alike in domestic and wild.

one animal by another of its kind seems to imply some
difference. The disposition of wild animals undoubtedly differs. The
variation, such as it is, chiefly affects the same parts in wild
organisms as in domestic breeds; for instance, the size, colour, and
the external and less important parts. In many species the variability
of certain organs or qualities is even stated as one of the specific
characters: thus, in plants, colour, size, hairiness, the number of the
stamens and pistils, and even their presence, the form of the leaves;
the size and form of the mandibles of the males of some insects; the
length and curvature of the beak in some birds (as in Opetiorynchus)
are variable characters in some species and quite fixed in others. I do
not perceive that any just distinction can be drawn between this
recognised variability of certain parts in many species and the more
general variability of the whole frame in domestic races.

Although the amount of variation be exceedingly small in
most organic beings in a state of nature, and probably quite wanting
(as far as our senses serve) in the majority of cases; yet considering
how many animals and plants, taken by mankind from different quarters
of the world for the most diverse purposes, have varied under
domestication in every country and in every age, I think we may safely
conclude that all organic beings with few exceptions, if capable of
being domesticated and bred for long periods, would vary. Domestication
seems to resolve itself into a change from the natural conditions of
the species [generally perhaps including an increase of food]; if this
be so, organisms in a state of nature must occasionally, in
the course of ages, be exposed to analogous influences; for geology
clearly shows that many places must, in the course of time, become
exposed to the widest range of climatic and other influences; and if
such places be isolated, so that

new and better adapted organic beings cannot freely
emigrate, the old inhabitants will be exposed to new influences,
probably far more varied, than man applies under the form of
domestication. Although every species no doubt will soon breed up to
the full number which the country will support, yet it is easy to
conceive that, on an average, some species may receive an increase of
food; for the times of dearth may be short, yet enough to kill, and
recurrent only at long intervals. All such changes of conditions from
geological causes would be exceedingly slow; what effect the slowness
might have we are ignorant; under domestication it appears that the
effects of change of conditions accumulate, and then break out.
Whatever might be the result of these slow geological changes, we may
feel sure, from the means of dissemination common in a lesser or
greater degree to every organism taken conjointly with the changes of
geology, which are steadily (and sometimes suddenly, as when an isthmus
at last separates) in progress, that occasionally organisms must
suddenly be introduced into new regions, where, if the conditions of
existence are not so foreign as to cause its extermination, it will
often be propagated under circumstances still more closely analogous to
those of domestication; and therefore we expect will evince a tendency
to vary. It appears to me quite inexplicable if this has
never happened; but it can happen very rarely. Let us then suppose that
an organism by some chance (which might be hardly repeated in 1000
years) arrives at a modern volcanic island in process of formation and
not fully stocked with the most appropriate organisms; the new organism
might readily gain a footing, although the external conditions were
considerably different from its native ones. The effect of this we
might expect would influence in some small degree the size, colour,
nature of covering &c., and from inexplicable influences

even special parts and organs of the body. But we might
further (and <this> is far more important) expect that the reproductive
system would be affected, as under domesticity, and the structure of
the offspring rendered in some degree plastic. Hence almost every part
of the body would tend to vary from the typical form in slight degrees,
and in no determinate way, and therefore without selection the
free crossing of these small variations (together with the tendency to
reversion to the original form) would constantly be counteracting this
unsettling effect of the extraneous conditions on the reproductive
system. Such, I conceive, would be the unimportant result without
selection. And here I must observe that the foregoing remarks are
equally applicable to that small and admitted amount of variation which
has been observed in some organisms in a state of nature; as well as to
the above hypothetical variation consequent on changes of condition.

Let us now suppose a Being1 with penetration
sufficient to perceive differences in the outer and innermost
organization quite imperceptible to man, and with forethought extending
over future centuries to watch with unerring care and select for any
object the offspring of an organism produced under the foregoing
circumstances; I can see no conceivable reason why he could not form a
new race (or several were he to separate the stock of the original
organism and work on several islands) adapted to new ends. As we assume
his discrimination, and his forethought, and his steadiness of object,
to be incomparably greater that those qualities in man, so we may
suppose the beauty and complications of the adaptations of the new
races and their differences from the original stock to be greater than
in the domestic races produced by man's agency: the

ground-work of his labours we may aid by supposing that
the external conditions of the volcanic island, from its continued
emergence and the occasional introduction of new immigrants, vary; and
thus to act on the reproductive system of the organism, on which he is
at work, and so keep its organization somewhat plastic. With time
enough, such a Being might rationally (without some unknown law opposed
him) aim at almost any result.

For instance, let this imaginary Being wish, from seeing a
plant growing on the decaying matter in a forest and choked by other
plants, to give it power of growing on the rotten stems of trees, he
would commence selecting every seedling whose berries were in the
smallest degree more attractive to tree-frequenting birds, so as to
cause a proper dissemination of the seeds, and at the same time he
would select those plants which had in the slightest degree more and
more power of drawing nutriment from rotten wood; and he would destroy
all other seedlings with less of this power. He might thus, in the
course of century after century, hope to make the plant by degrees grow
on rotten wood, even high up on trees, wherever birds dropped the
non-digested seeds. He might then, if the organization of the plant was
plastic, attempt by continued selection of chance seedlings to make it
grow on less and less rotten wood, till it would grow on sound wood1.
Supposing again, during these changes the plant failed to seed quite
freely from non-impregnation, he might begin selecting seedlings with a
little sweeter <or> differently tasted honey or pollen, to tempt
insects to visit the flowers regularly: having effected this, he might
wish, if it profited the plant, to render abortive the stamens and
pistils in different flowers, which he could do by continued selection.
By such

1 The mistletoe is used as an
illustration in Origin, Ed. i. p. 3, vi. p. 3, but with less
detail.

steps he might aim at making a plant as wonderfully
related to other organic beings as is the mistletoe, whose existence
absolutely depends on certain insects for impregnation, certain birds
for transportal, and certain trees for growth. Furthermore, if the
insect which had been induced regularly to visit this hypothetical
plant profited much by it, our same Being might wish by selection to
modify by gradual selection the insect's structure, so as to facilitate
its obtaining the honey or pollen: in this manner he might adapt the
insect (always presupposing its organization to be in some degree
plastic) to the flower, and the impregnation of the flower to the
insect; as is the case with many bees and many plants.

Seeing what blind capricious man has actually effected by
selection during the few last years, and what in a ruder state he has
probably effected without any systematic plan during the last few
thousand years, he will be a bold person who will positively put limits
to what the supposed Being could effect during whole geological
periods. In accordance with the plan by which this universe seems
governed by the Creator, let us consider whether there exists any secondary means in the economy of nature by which the process of selection
could go on adapting, nicely and wonderfully, organisms, if in ever so
small a degree plastic, to diverse ends. I believe such secondary means
do exist1.

Natural means of Selection2.

De Candolle, in an eloquent passage, has declared that all
nature is at war, one organism with another,

1 <Note in original.> The
selection, in cases where adult lives only few hours as Ephemera, must
fall on larva—curious
speculation of the effect <which> changes in it
would bring in parent.

2 This section forms part of the
joint paper by Darwin and Wallace read before the Linnean Society on
July 1, 1858.

or with external nature. Seeing the contented face of
nature, this may at first be well doubted; but reflection will
inevitably prove it is too true. The war, however, is not constant, but
only recurrent in a slight degree at short periods and more severely at
occasional more distant periods; and hence its effects are easily
overlooked. It is the doctrine of Malthus applied in most cases with
ten-fold force. As in every climate there are seasons for each of its
inhabitants of greater and less abundance, so all annually breed; and
the moral restraint, which in some small degree checks the increase of
mankind, is entirely lost. Even slow-breeding mankind has doubled in 25
years1, and if he could increase his food with greater ease,
he would double in less time. But for animals, without artificial
means, on an average the amount of food for each species
must be constant; whereas the increase of all organisms tends to be
geometrical, and in a vast majority of cases at an enormous ratio.
Suppose in a certain spot there are eight pairs of [robins] birds, and
that only four pairs of them annually (including double
hatches) rear only four young; and that these go on rearing their young
at the same rate: then at the end of seven years (a short life,
excluding violent deaths, for any birds) there will be 2048 robins,
instead of the original sixteen; as this increase is quite impossible,
so we must conclude either that robins do not rear nearly half their
young or that the average life of a robin when reared is from accident
not nearly seven years. Both checks probably concur. The same kind of
calculation applied to all vegetables and animals produces results
either more or less striking, but in scarcely a single instance less
striking than in man2.

to increase are on record, namely during peculiar seasons,
in the extraordinary increase of certain animals, for instance during
the years 1826 to 1828, in La Plata, when from drought, some millions
of cattle perished, the whole country swarmed with
innumerable mice: now I think it cannot be doubted that during the
breeding season all the mice (with the exception of a few males or
females in excess) ordinarily pair; and therefore that this astounding
increase during three years must be attributed to a greater than usual
number surviving the first year, and then breeding, and so on, till the
third year, when their numbers were brought down to their usual limits
on the return of wet weather. Where man has introduced plants and
animals into a new country favourable to them, there are many accounts
in how surprisingly few years the whole country has become stocked with
them. This increase would necessarily stop as soon as the country was
fully stocked; and yet we have every reason to believe from what is
known of wild animals that all would pair in the spring. In
the majority of cases it is most difficult to imagine where the check
falls, generally no doubt on the seeds, eggs, and young; but when we
remember how impossible even in mankind (so much better known than any
other animal) it is to infer from repeated casual observations what the
average of life is, or to discover how different the percentage of
deaths to the births in different countries, we ought to feel no
legitimate surprise at not seeing where the check falls in animals and
plants. It should always be remembered that in most cases the checks
are yearly recurrent in a small regular degree, and in an extreme
degree during occasionally unusually cold, hot, dry, or wet years,
according to the constitution of the being in question. Lighten any
check in the smallest degree, and the geo-

metrical power of increase in every organism will
instantly increase the average numbers of the favoured species. Nature
may be compared to a surface, on which rest ten thousand sharp wedges
touching each other and driven inwards by incessant blows1.
Fully to realise these views much reflection is requisite; Malthus on
man should be studied; and all such cases as those of the mice in La
Plata, of the cattle and horses when first turned out in S. America, of
the robins by our calculation, &c., should be well considered:
reflect on the enormous multiplying power inherent and annually in
action in all animals; reflect on the countless seeds scattered
by a hundred ingenious contrivances, year after year, over the whole
face of the land; and yet we have every reason to suppose that the
average percentage of every one of the inhabitants of a country will ordinarily remain constant. Finally, let it be borne in mind that this
average number of individuals (the external conditions remaining the
same) in each country is kept up by recurrent struggles against other
species or against external nature (as on the borders of the arctic
regions2, where the cold checks life); and that ordinarily
each individual of each species holds its place, either by its own
struggle and capacity of acquiring nourishment in some period (from the
egg upwards) of its life, or by the struggle of its parents (in short
lived organisms, when the main check occurs at long intervals) against
and compared with other individuals of the same or different species.

But let the external conditions of a country change; if in
a small degree, the relative proportions of the inhabitants will in
most cases simply be

1 This simile occurs in Origin,
Ed. i. p. 67, not in the later editions.

2 <Note in the original.> In
case like mistletoe, it may be asked why not more species, no other
species interferes; answer almost sufficient, same causes which check
the multiplication of individuals.

slightly changed; but let the number of inhabitants be
small, as in an island1, and free access to it from other
countries be circumscribed; and let the change of condition continue
progressing (forming new stations); in such case the original
inhabitants must cease to be so perfectly adapted to the changed
conditions as they originally were. It has been shown that probably
such changes of external conditions would, from acting on the
reproductive system, cause the organization of the beings most affected
to become, as under domestication, plastic. Now can it be doubted from
the struggle each individual (or its parents) has to obtain subsistence
that any minute variation in structure, habits, or instincts, adapting
that individual better to the new conditions, would tell upon its
vigour and health? In the struggle it would have a better chance of
surviving, and those of its offspring which inherited the variation,
let it be ever so slight, would have a better chance to
survive. Yearly more are bred than can survive; the smallest grain in
the balance, in the long run, must tell on which death shall fall, and
which shall survive2. Let this work of selection, on the one
hand, and death on the other, go on for a thousand generations; who
would pretend to affirm that it would produce no effect, when we
remember what in a few years Bakewell effected in cattle and Western in
sheep, by this identical principle of selection.

To give an imaginary example, from changes in progress on
an island, let the organization3 of a canine animal become
slightly plastic, which animal preyed chiefly on rabbits, but sometimes
on hares; let these same changes cause the number of rabbits

1 See Origin, Ed. i.
pp. 104, 292, vi. pp. 127, 429.

2 Recognition of the importance of minute
differences in the struggle occurs in the Essay of 1842, p. 8 note 3.

very slowly to decrease and the number of hares to
increase; the effect of this would be that the fox or dog would be
driven to try to catch more hares, and his numbers would tend to
decrease; his organization, however, being slightly plastic, those
individuals with the lightest forms, longest limbs, and best eyesight
(though perhaps with less cunning or scent) would be slightly favoured,
let the difference be ever so small, and would tend to live longer and
to survive during that time of the year when food was shortest; they
would also rear more young, which young would tend to inherit these
slight peculiarities. The less fleet ones would be rigidly destroyed. I
can see no more reason to doubt but that these causes in a thousand
generations would produce a marked effect, and adapt the form of the
fox to catching hares instead of rabbits, than that greyhounds can be
improved by selection and careful breeding. So would it be with plants
under similar circumstances; if the number of individuals of a species
with plumed seeds could be increased by greater powers of dissemination
within its own area (that is if the check to increase fell chiefly on
the seeds), those seeds which were provided with ever so little more
down, or with a plume placed so as to be slightly more acted on by the
winds, would in the long run tend to be most disseminated; and hence a
greater number of seeds thus formed would germinate, and would tend to
produce plants inheriting this slightly better adapted down.

Besides this natural means of selection, by which those
individuals are preserved, whether in their egg or seed or in their
mature state, which are best adapted to the place they fill in nature,
there is a second agency at work in most bisexual animals tending to
produce the same effect, namely the struggle of the males for the
females. These struggles are generally decided by the law of battle;

but in the case of birds, apparently, by the charms of
their song1, by their beauty or their power of courtship, as
in the dancing rock-thrush of Guiana. Even in the animals which pair
there seems to be an excess of males which would aid in causing a
struggle: in the polygamous animals2, however, as in deer,
oxen, poultry, we might expect there would be severest struggle: is it
not in the polygamous animals that the males are best formed for mutual
war? The most vigorous males, implying perfect adaptation, must
generally gain the victory in their several contests. This kind of
selection, however, is less rigorous than the other; it does not
require the death of the less successful, but gives to them fewer
descendants. This struggle falls, moreover, at a time of year when food
is generally abundant, and perhaps the effect chiefly produced would be
the alteration of sexual characters, and the selection of individual
forms, no way related to their power of obtaining food, or of defending
themselves from their natural enemies, but of fighting one with
another. This natural struggle amongst the males may be compared in
effect, but in a less degree, to that produced by those
agriculturalists who pay less attention to the careful selection of all
the young animals which they breed and more to the occasional use of a
choice male3.

1 These two forms of sexual
selection are given in Origin, Ed. i. p. 87, vi. p. 107. The
Guiana rock-thrush is given as an example of bloodless competition.

2 <Note in original.> Seals?
Pennant about battles of seals.

3 In the Linnean paper of July
1, 1858 the final word is mate: but the context shows that it
should be male; it is moreover clearly so written in the MS.

Differences between
"Races" and
"Species":—first, in their trueness or variability.

Races1 produced by these natural means of
selection2 we may expect would differ in some respects from
those produced by man. Man selects chiefly by the eye, and is not able
to perceive the course of every vessel and nerve, or the form of the
bones, or whether the internal structure corresponds to the outside
shape. He3 is unable to select shades of constitutional
differences, and by the protection he affords and his endeavours to
keep his property alive, in whatever country he lives, he checks, as
much as lies in his power, the selecting action of nature, which will,
however, go on to a lesser degree with all living things, even if their
length of life is not determined by their own powers of endurance. He
has bad judgment, is capricious, he does not, or his successors do not,
wish to select for the same exact end for hundreds of generations. He
cannot always suit the selected form to the properest conditions; nor
does he keep those conditions uniform: he selects that which is useful
to him, not that best adapted to those conditions in which each variety
is placed by him: he selects a small dog, but feeds it highly; he
selects a long-backed dog, but does not exercise it in any peculiar
manner, at least not during every generation. He seldom allows the most
vigorous males to struggle for themselves and propagate, but picks out
such as he possesses, or such as he prefers, and not necessarily those
best adapted to the existing conditions. Every agriculturalist and
breeder knows how difficult it is to prevent an occasional cross with
another breed.

1 In the Origin the
author would here have used the word variety.

2 The whole of p. 94 and 15
lines of p. 95 are, in the MS., marked through in
pencil with vertical lines, beginning at "Races produced, &c." and
ending with "to these conditions."

He often grudges to destroy an individual which departs
considerably from the required type. He often begins his selection by a
form or sport considerably departing from the parent form. Very
differently does the natural law of selection act; the varieties
selected differ only slightly from the parent forms1; the
conditions are constant for long periods and change slowly; rarely can
there be a cross; the selection is rigid and unfailing, and continued
through many generations; a selection can never be made without
the form be better adapted to the conditions than the parent
form; the selecting power goes on without caprice, and steadily for
thousands of years adapting the form to these conditions. The selecting
power is not deceived by external appearances, it tries the being
during its whole life; and if less well <?> adapted than its congeners, without fail it is destroyed; every part of its structure is thus
scrutinised and proved good towards the place in nature which it
occupies.

We have every reason to believe that in proportion to the
number of generations that a domestic race is kept free from crosses,
and to the care employed in continued steady selection with one end in
view, and to the care in not placing the variety in conditions unsuited
to it; in such proportion does the new race become "true" or subject to
little variation2. How incomparably "truer" then would a
race produced by the above rigid, steady, natural means of selection,
excellently trained and perfectly adapted to its conditions, free from
stains of blood or crosses, and continued during thousands of years, be
compared with one produced by the feeble, capri-

1 In the present Essay there is
some evidence that the author attributed more to sports than
was afterwards the case: but the above passage points the other way. It
must always be remembered that many of the minute differences, now
considered small mutations, are the small variations on which Darwin
conceived selection to act.

cious, misdirected and ill-adapted selection of man. Those
races of domestic animals produced by savages, partly by the inevitable
conditions of their life, and partly unintentionally by their greater
care of the individuals most valuable to them, would probably approach
closest to the character of a species; and I believe this is the case.
Now the characteristic mark of a species, next, if not equal in
importance to its sterility when crossed with another species, and
indeed almost the only other character (without we beg the question and
affirm the essence of a species, is its not having descended from a
parent common to any other form), is the similarity of the individuals
composing the species, or in the language of agriculturalists their
"trueness."

Difference between "Races" and "Species" in fertility when crossed.

The sterility of species, or of their offspring, when
crossed has, however, received more attention than the uniformity in
character of the individuals composing the species. It is exceedingly
natural that such sterility1 should have been long thought
the certain characteristic of species. For it is obvious that if the
allied different forms which we meet with in the same country could
cross together, instead of finding a number of distinct species, we
should have a confused and blending series. The fact however of a
perfect gradation in the degree of sterility between species, and the
circumstance of some species most closely allied (for instance many
species of crocus and European heaths) refusing

1 <Note in the original.> If
domestic animals are descended from several species and become fertile inter se, then one can see they gain fertility by becoming
adapted to new conditions and certainly domestic animals can withstand
changes of climate without loss of fertility in an astonishing manner.

to breed together, whereas other species, widely
different, and even belonging to distinct genera, as the fowl and the
peacock, pheasant and grouse1, Azalea and Rhododendron,
Thuja and Juniperus, breeding together ought to have caused a doubt
whether the sterility did not depend on other causes, distinct from a
law, coincident with their creation. I may here remark that the fact
whether one species will or will not breed with another is far less
important than the sterility of the offspring when produced; for even
some domestic races differ so greatly in size (as the great
stag-greyhound and lap-dog, or cart-horse and Burmese ponies) that
union is nearly impossible; and what is less generally known is, that
in plants Kölreuter has shown by hundreds of experiments that the
pollen of one species will fecundate the germen of another species,
whereas the pollen of this latter will never act on the germen of the
former; so that the simple fact of mutual impregnation certainly has no
relation whatever to the distinctness in creation of the two forms.
When two species are attempted to be crossed which are so distantly
allied that offspring are never produced, it has been observed in some
cases that the pollen commences its proper action by exserting its
tube, and the germen commences swelling, though soon afterwards it
decays. In the next stage in the series, hybrid offspring are produced
though only rarely and few in number, and these are absolutely sterile:
then we have hybrid offspring more numerous, and occasionally, though
very rarely, breeding with either parent, as is the case with the
common mule. Again, other hybrids, though infertile inter se,
will breed quite freely with either parent, or with a third
species, and will yield

1 See Suchetet, L'Hybridité
dans la Nature, Bruxelles, 1888, p. 67. In Var. under Dom.,
Ed. ii. vol. II. hybrids between the fowl and the
pheasant are
mentioned. I can give no information on the other cases.

offspring generally infertile, but sometimes fertile; and
these latter again will breed with either parent, or with a third or
fourth species: thus Kölreuter blended together many forms. Lastly it
is now admitted by those botanists who have longest contended against
the admission, that in certain families the hybrid offspring of many of
the species are sometimes perfectly fertile in the first generation
when bred together: indeed in some few cases Mr Herbert1 found that the hybrids were decidedly more fertile than either of their
pure parents. There is no way to escape from the admission that the
hybrids from some species of plants are fertile, except by declaring
that no form shall be considered as a species, if it produces with
another species fertile offspring: but this is begging the question2.
It has often been stated that different species of animals have a
sexual repugnance towards each other; I can find no evidence of this;
it appears as if they merely did not excite each others passions. I do
not believe that in this respect there is any essential distinction
between animals and plants; and in the latter there cannot be a feeling
of repugnance.

Causes of Sterility in
Hybrids.

The difference in nature between species which causes the
greater or lesser degree of sterility in their offspring appears,
according to Herbert and Kölreuter, to be connected much less with
external form, size, or structure, than with constitutional
peculiarities; by which is meant their adaptation to different
climates, food and situation, &c.: these

1Origin, Ed. i. p.
250, vi. p. 370.

2 This was the position of
Gärtner and of Kölreuter: see Origin, Ed. i. pp. 246-7, vi.
pp. 367-8.

peculiarities of constitution probably affect the entire
frame, and no one part in particular1.

From the foregoing facts I think we must admit that there
exists a perfect gradation in fertility between species which when
crossed are quite fertile (as in Rhododendron, Calceolaria, &c.),
and indeed in an extraordinary degree fertile (as in Crinum), and those
species which never produce offspring, but which by certain effects (as
the exsertion of the pollen-tube) evince their alliance. Hence, I
conceive, we must give up sterility, although undoubtedly in a lesser
or greater degree of very frequent occurrence, as an unfailing mark by
which species can be distinguished from races, i.e. from
those forms which have descended from a common stock.

Infertility from causes
distinct from
hybridisation.

Let us see whether there are any analogous facts which
will throw any light on this subject, and will tend to explain why the
offspring of certain species, when crossed, should be sterile, and not
others, without requiring a distinct law connected with their creation
to that effect. Great numbers, probably a large majority of animals
when caught by man and removed from their natural conditions, although
taken very young, rendered quite tame, living to a good old age, and
apparently quite healthy, seem incapable under these circumstances of
breeding2. I do not refer to animals kept in

1 <Note in the original.> Yet
this seems introductory to the case of the heaths and crocuses above
mentioned. <Herbert observed that crocus does not set seed if
transplanted before pollination, but that such treatment after
pollination has no sterilising effect. (Var. under Dom., Ed.
ii. vol. II. p. 148.) On the same page is a mention of
the Ericaceæ
being subject to contabescence of the anthers. For Crinum see Origin, Ed. i. p. 250: for Rhododenron and Calceolaria see p. 251.>

menageries, such as at the Zoological Gardens, many of
which, however, appear healthy and live long and unite but do not
produce; but to animals caught and left partly at liberty in their
native country. Rengger1 enumerates several caught young and
rendered tame, which he kept in Paraguay, and which would not breed:
the hunting leopard or cheetah and elephant offer other instances; as
do bears in Europe, and the 25 species of hawks, belonging to different
genera, thousands of which have been kept for hawking and have lived
for long periods in perfect vigour. When the expense and trouble of
procuring a succession of young animals in a wild state be borne in
mind, one may feel sure that no trouble has been spared in endeavours
to make them breed. So clearly marked is this difference in different
kinds of animals, when captured by man, that St Hilaire makes two great
classes of animals useful to man:—the tame, which will not
breed, and the domestic which will breed in domestication.
>From certain singular facts we might have supposed that the
non-breeding of animals was owing to some perversion of instinct. But
we meet with exactly the same class of facts in plants: I do not refer
to the large number of cases where the climate does not permit the seed
or fruit to ripen, but where the flowers do not "set," owing to some
imperfection of the ovule or pollen. The latter, which alone can be
distinctly examined, is often manifestly imperfect, as any one with a
microscope can observe by comparing the pollen of the Persian and
Chinese lilacs2 with the common lilac; the two

taken out of their native condition than
plants, and so are more sterile when crossed.

We have one broad fact that sterility in
hybrids is not closely related to external difference, and these are
what man alone gets by selection.

1 See Var. under Dom., Ed.
ii. vol. II. p. 132; for the case of the cheetah see loc
cit. p.
133.

former species (I may add) are equally sterile in Italy as
in this country. Many of the American bog plants here produce little or
no pollen, whilst the Indian species of the same genera freely produce
it. Lindley observes that sterility is the bane of the horticulturist1:
Linnæus has remarked on the sterility of nearly all alpine flowers
when cultivated in a lowland district2. Perhaps the immense
class of double flowers chiefly owe their structure to an excess of
food acting on parts rendered slightly sterile and less capable of
performing their true function, and therefore liable to be rendered
monstrous, which monstrosity, like any other disease, is inherited and
rendered common. So far from domestication being in itself unfavourable
to fertility, it is well known that when an organism is once capable of
submission to such conditions <its> fertility is increased3 beyond the natural limit. According to agriculturists, slight changes
of conditions, that is of food or habitation, and likewise crosses with
races slightly different, increase the vigour and probably the
fertility of their offspring. It would appear also that even a great
change of condition, for instance, transportal from temperate countries
to India, in many cases does not in the least affect fertility,
although it does health and length of life and the period of maturity.
When sterility is induced by domestication it is of the same kind, and
varies in degree, exactly as with hybrids: for be it remembered that
the most sterile hybrid is no way monstrous; its organs are perfect,
but they do not act, and minute microscopical investigations show that
they are in the same state as those of pure species in the intervals of
the breeding season. The defective pollen in the cases above alluded to
pre-

cisely resembles that of hybrids. The occasional breeding
of hybrids, as of the common mule, may be aptly compared to the most
rare but occasional reproduction of elephants in captivity. The cause
of many exotic Geraniums producing (although in vigorous health)
imperfect pollen seems to be connected with the period when water is
given them1; but in the far greater majority of
cases we cannot form any conjecture on what exact cause the sterility
of organisms taken from their natural conditions depends. Why, for
instance, the cheetah will not breed whilst the common cat and ferret
(the latter generally kept shut up in a small box) do,—why the elephant
will not whilst the pig will abundantly—why
the partridge and grouse in their own country will not, whilst several
species of pheasants, the guinea-fowl from the deserts of Africa and
the peacock from the jungles of India, will. We must, however, feel
convinced that it depends on some constitutional peculiarities in these
beings not suited to their new condition; though not necessarily
causing an ill state of health. Ought we then to wonder much that those
hybrids which have been produced by the crossing of species with
different constitutional tendencies (which tendencies we know to be
eminently inheritable) should be sterile: it does not seem improbable
that the cross from an alpine and lowland plant should have its
constitutional powers deranged, in nearly the same manner as when the
parent alpine plant is brought into a lowland district. Analogy,
however, is a deceitful guide, and it would be rash to affirm, although
it may appear probable, that the sterility of hybrids is due to the
constitutional peculiarities of one parent being disturbed by being
blended with those of the other parent in exactly the same

manner as it is caused in some organic beings when placed
by man out of their natural conditions1. Although this would
be rash, it would, I think, be still rasher, seeing that sterility is
no more incidental to all cross-bred productions than it is
to all organic beings when captured by man, to assert that the
sterility of certain hybrids proved a distinct creation of their
parents.

But it may be objected2 (however little the
sterility of certain hybrids is connected with the distinct creations
of species), how comes it, if species are only races produced by
natural selection, that when crossed they so frequently produce sterile
offspring, whereas in the offspring of those races confessedly produced
by the arts of man there is no one instance of sterility. There is not
much difficulty in this, for the races produced by the natural means
above explained will be slowly but steadily selected; will be adapted
to various and diverse conditions, and to these conditions they will be
rigidly confined for immense periods of time; hence we may suppose that
they would acquire different constitutional peculiarities adapted to
the stations they occupy; and on the constitutional differences between
species their sterility, according to the best authorities, depends. On
the other hand man selects by external appearance3; from his
ignorance, and from not having any test at least comparable in delicacy
to the natural struggle for food, continued at intervals through the
life of each individual, he cannot eliminate fine shades of
constitution, dependent on invisible differences in the fluids or
solids of the body; again, from the value

1Origin, Ed. i. p.
267, vi. p. 392. This is the principle experimentally investigated in
the author's Cross- and Self-Fertilisation.

2Origin, Ed. i. p.
268, vi. p. 398.

3 <Notes in original.> Mere
difference of structure no guide to what will or will not cross. First
step gained by races keeping apart. <It is not clear where these notes
were meant to go.>

which he attaches to each individual, he asserts his
utmost power in contravening the natural tendency of the most vigorous
to survive. Man, moreover, especially in the earlier ages, cannot have
kept his conditions of life constant, and in later ages his stock pure.
Until man selects two varieties from the same stock, adapted to two
climates or to other different external conditions, and confines each
rigidly for one or several thousand years to such conditions, always
selecting the individuals best adapted to them, he cannot be said to
have even commenced the experiment. Moreover, the organic beings which
man has longest had under domestication have been those which were of
the greatest use to him, and one chief element of their usefulness,
especially in the earlier ages, must have been their capacity to
undergo sudden transportals into various climates, and at the same time
to retain their fertility, which in itself implies that in such
respects their constitutional peculiarities were not closely limited.
If the opinion already mentioned be correct, that most of the domestic
animals in their present state have descended from the fertile
commixture of wild races or species, we have indeed little reason now
to expect infertility between any cross of stock thus descended.

It is worthy of remark, that as many organic beings, when
taken by man out of their natural conditions, have their reproductive
system <so> affected as to be incapable of propagation, so, we saw in
the first chapter, that although organic beings when taken by man do
propagate freely, their offspring after some generations vary or sport
to a degree which can only be explained by their reproductive system
being <in> some way affected. Again, when species cross, their
offspring are generally sterile; but it was found by Kölreuter that
when hybrids are capable of breeding with either parent, or with

other species, that their offspring are subject after some
generations to excessive variation1. Agriculturists, also,
affirm that the offspring from mongrels, after the first generation,
vary much. Hence we see that both sterility and variation in the
succeeding generations are consequent both on the removal of individual
species from their natural states and on species crossing. The
connection between these facts may be accidental, but they certainly
appear to elucidate and support each other,—on the principle of the
reproductive system of all organic beings being eminently sensitive to
any disturbance, whether from removal or commixture, in their
constitutional relations to the conditions to which they are exposed.

Points of Resemblance
between "Races" and"Species2."

Races and reputed species agree in some respects, although
differing from causes which, we have seen, we can in some degree
understand, in the fertility and "trueness" of their offspring. In the
first place, there is no clear sign by which to distinguish races from
species, as is evident from the great difficulty experienced by
naturalists in attempting to discriminate them. As far as external
characters are concerned, many of the races which are descended from
the same stock differ far more than true species of the same genus;
look at the willow-wrens, some of which skilful ornithologists can
hardly distinguish from each other except by their nests; look at the
wild swans, and compare the distinct species of these genera with the
races of

1Origin, Ed. i. p.
272, vi. p. 404.

2 This section seems not to
correspond closely with any in the Origin, Ed. i.; in some
points it resembles pp. 15, 16, also the section on analogous variation
in distinct species, Origin, Ed. i. p. 159, vi. p. 194.

domestic ducks, poultry, and pigeons; and so again with
plants, compare the cabbages, almonds, peaches and nectarines, &c.
with the species of many genera. St Hilaire has even remarked that
there is a greater difference in size between races, as in dogs (for he
believes all have descended from one stock), than between the species
of any one genus; nor is this surprising, considering that amount of
food and consequently of growth is the element of change over which man
has most power. I may refer to a former statement, that breeders
believe the growth of one part or strong action of one function causes
a decrease in other parts; for this seems in some degree analogous to
the law of "organic compensation1," which many naturalists
believe holds good. To give an instance of this law of
compensation,—those species of Carnivora which have the canine teeth
greatly
developed have certain molar teeth deficient; or again, in that
division of the Crustaceans in which the tail is much developed, the
thorax is little so, and the converse. The points of difference between
different races is often strikingly analogous to that between species
of the same genus: trifling spots or marks of colour2 (as
the bars on pigeons' wings) are often preserved in races of plants and
animals, precisely in the same manner as similar trifling characters
often pervade all the species of a genus, and even of a family. Flowers
in varying their colours often become veined and spotted and the leaves
become divided like true species: it is known that the varieties of the
same plant never have red, blue and yellow flowers, though the hyacinth
makes a very near approach to an

1 The law of compensation is
discussed in the Origin, Ed. i. p. 147, vi. p. 182.

2 <Note in original.> Boitard
and Corbié on outer edging red in tail of bird,—so bars on wing, white
or black or brown, or white edged with black or <illegible>: analogous
to marks running through genera but with different colours. Tail
coloured in pigeons.

exception1; and different species of the same
genus seldom, though sometimes they have flowers of these three
colours. Dun-coloured horses having a dark stripe down their backs, and
certain domestic asses having transverse bars on their legs, afford
striking examples of a variation analogous in character to the
distinctive marks of other species of the same genus.

External characters of
Hybrids and
Mongrels.

There is, however, as it appears to me, a more important
method of comparison between species and races, namely the character of
the offspring2 when species are crossed and when races are
crossed: I believe, in no one respect, except in sterility, is there
any difference. It would, I think, be a marvellous fact, if species
have been formed by distinct acts of creation, that they should act
upon each other in uniting, like races descended from a common stock.
In the first place, by repeated crossing one species can absorb and
wholly obliterate the characters of another, or of several other
species, in the same manner as one race will absorb by crossing another
race. Marvellous, that one act of creation should absorb another or
even several acts of creation! The offspring of species, that is
hybrids, and the offspring of races, that is mongrels, resemble each
other in being either intermediate in character (as is most frequent in
hybrids) or in resembling sometimes closely one and sometimes the other
parent; in both the offspring produced by the same act of conception
sometimes differ in their

2 This section corresponds
roughly to that on Hybrids and Mongrels compared independently of
their fertility, Origin, Ed. i. p. 272, vi. p. 403. The discussion
on Gärtner's views, given in the Origin, is here wanting. The
brief mention of prepotency is common to them both.

degree of resemblance; both hybrids and mongrels sometimes
retain a certain part or organ very like that of either parent, both,
as we have seen, become in succeeding generations variable; and this
tendency to vary can be transmitted by both; in both for many
generations there is a strong tendency to reversion to their ancestral
form. In the case of a hybrid laburnum and of a supposed mongrel vine
different parts of the same plants took after each of their two
parents. In the hybrids from some species, and in the mongrel of some
races, the offspring differ according as which of the two species, or
of the two races, is the father (as in the common mule and hinny) and
which the mother. Some races will breed together, which differ so
greatly in size, that the dam often perishes in labour; so it is with
some species when crossed; when the dam of one species has borne
offspring to the male of another species, her succeeding offspring are
sometimes stained (as in Lord Morton's mare by the quagga, wonderful as
the fact1 is) by this first cross; so agriculturists
positively affirm is the case when a pig or sheep of one breed has
produced offspring by the sire of another breed.

Summary of second chapter2.

Let us sum up this second chapter. If slight variations do
occur in organic beings in a state of nature; if changes of condition
from geological causes do produce in the course of ages effects
analogous to those of domestication on any, however few, organisms; and
how can we doubt it,—from what is actually known, and from what may be
presumed, since thousands of organisms taken by man

1 See Animals and Plants, Ed.
ii. vol. I. p. 435. The phenomenon of Telegony,
supposed to
be established by this and similar cases, is now generally discredited
in consequence of Ewart's experiments.

for sundry uses, and placed in new conditions, have
varied. If such variations tend to be hereditary; and how can we doubt
it,—when we see shades of expression, peculiar manners, monstrosities
of the strangest kinds, diseases, and a multitude of other
peculiarities, which characterise and form, being inherited, the
endless races (there are 1200 kinds of cabbages1) of our
domestic plants and animals. If we admit that every organism maintains
its place by an almost periodically recurrent struggle; and how can we
doubt it,—when we know that all beings tend to increase in a
geometrical ratio (as is instantly seen when the conditions become for
a time more favourable); whereas on an average the amount of food must
remain constant, if so, there will be a natural means of selection,
tending to preserve those individuals with any slight deviations of
structure more favourable to the then existing conditions, and tending
to destroy any with deviations of an opposite nature. If the above
propositions be correct, and there be no law of nature limiting the
possible amount of variation, new races of beings will,—perhaps only
rarely, and only in some few districts,—be formed.

Limits of Variation.

That a limit to variation does exist in nature is assumed
by most authors, though I am unable to discover a single fact on which
this belief is grounded2. One of the commonest statements is
that plants do not become acclimatised; and I have even observed that
kinds not raised by seed, but propagated by cuttings, &c., are
instanced. A good instance has, however, been advanced in the case of
kidney beans, which it is believed are now as

tender as when first introduced. Even if we overlook the
frequent introduction of seed from warmer countries, let me observe
that as long as the seeds are gathered promiscuously from the bed,
without continual observation and careful selection of those
plants which have stood the climate best during their whole growth, the
experiment of acclimatisation has hardly been begun. Are not all those
plants and animals, of which we have the greatest number of races, the
oldest domesticated? Considering the quite recent progress1 of systematic agriculture and horticulture, is it not opposed to every
fact, that we have exhausted the capacity of variation in our cattle
and in our corn,—even if we have done so in some trivial points, as
their fatness or kind of wool? Will any one say, that if horticulture
continues to flourish during the next few centuries, that we shall not
have numerous new kinds of the potato and Dahlia? But take two
varieties of each of these plants, and adapt them to certain fixed
conditions and prevent any cross for 5000 years, and then again vary
their conditions; try many climates and situations; and who2 will predict the number and degrees of difference which might arise
from these stocks? I repeat that we know nothing of any limit to the
possible amount of variation, and therefore to the number and
differences of the races, which might be produced by the natural means
of selection, so infinitely more efficient than the agency of man.
Races thus produced would probably be very "true"; and if from having
been adapted to different conditions of existence, they possessed
different constitutions, if suddenly removed to some new station, they
would perhaps be sterile and their offspring would perhaps be infertile.

1 <Note in original.> History of
pigeons shows increase of peculiarities during last years.

Such races would be undistinguishable from species. But is
there any evidence that the species, which surround us on all sides,
have been thus produced? This is a question which an examination of the
economy of nature we might expect would answer either in the
affirmative or negative1.

1 <Note in original.> Certainly
<two pages in the MS.> ought to be here introduced,
viz., difficulty in
forming such organ, as eye, by selection. <In the Origin, Ed.
i., a chapter on Difficulties on Theory follows that on Laws
of Variation, and precedes that on Instinct: this was
also the arrangement in the Essay of 1842; whereas in the present Essay Instinct follows Variation and precedes Difficulties.>

ON THE VARIATION OF INSTINCTS AND OTHER
MENTAL ATTRIBUTES UNDER DOMESTICATION AND IN STATE OF NATURE; ON THE
DIFFICULTIES IN THIS SUBJECT; AND ON ANALOGOUS DIFFICULTIES WITH
RESPECT TO CORPOREAL STRUCTURES

Variation of mental
attributes under domestication.

I HAVE as yet only alluded to the mental qualities which
differ greatly in different species. Let me here premise that, as will
be seen in the Second Part, there is no evidence and consequently no
attempt to show that all existing organisms have descended
from any one common parent-stock, but that only those have so descended
which, in the language of naturalists, are clearly related to each
other. Hence the facts and reasoning advanced in this chapter do not
apply to the first origin of the senses1, or of the chief
mental attributes, such as of memory, attention, reasoning, &c.,
&c., by which most or all of the great related groups are
characterised, any more than they apply to the first origin of life, or
growth, or the power of reproduction. The application of such facts as
I have collected is merely to the differences of the primary mental
qualities and of the instincts in the species2 of the

1 A similar proviso occurs in
the chapter on instinct in Origin, Ed. i. p. 207, vi. p. 319.

2 The discussion occurs later in
Chapter VII of the Origin, Ed. i. than in the present Essay,
where moreover it is fuller in some respects.

several great groups. In domestic animals every observer
has remarked in how great a degree, in the individuals of the same
species, the dispositions, namely courage, pertinacity, suspicion,
restlessness, confidence, temper, pugnaciousness, affection, care of
their young, sagacity, &c., &c., vary. It would require a most
able metaphysician to explain how many primary qualities of the mind
must be changed to cause these diversities of complex dispositions.
>From these dispositions being inherited, of which the testimony is
unanimous, families and breeds arise, varying in these respects. I may
instance the good and ill temper of different stocks of bees and of
horses,—the pugnacity and courage of game fowls,—the pertinacity of
certain dogs, as bull-dogs, and the sagacity of others,—for
restlessness and suspicion compare a wild rabbit reared with the
greatest care from its earliest age with the extreme tameness of the
domestic breed of the same animal. The offspring of the domestic dogs
which have run wild in Cuba1, though caught quite young, are
most difficult to tame, probably nearly as much so as the original
parent-stock from which the domestic dog descended. The habitual "periods"
of different families of the same species differ, for instance, in the
time of year of reproduction, and the period of life when the capacity
is acquired, and the hour of roosting (in Malay fowls), &c.,
&c. These periodical habits are perhaps essentially corporeal, and
may be compared to nearly similar habits in plants, which are known to
vary extremely. Consensual movements (as called by Müller) vary and are
inherited,—such as the cantering and ambling paces in horses, the
tumbling of pigeons, and perhaps the handwriting, which is sometimes so
similar between father

1 In the margin occurs the name
of Poeppig. In Var. under Dom., Ed. ii. vol. I.
p. 28, the reference to Poeppig on the Cuban dogs contains no mention
of the wildness of their offspring.

and sons, may be ranked in this class. Manners,
and even tricks which perhaps are only peculiar manners,
according to W. Hunter and my father, are distinctly inherited in cases
where children have lost their parent in early infancy. The inheritance
of expression, which often reveals the finest shades of character, is
familiar to everyone.

Again the tastes and pleasures of different breeds vary,
thus the shepherd-dog delights in chasing the sheep, but has no wish to
kill them,—the terrier (see Knight) delights in killing vermin, and the
spaniel in finding game. But it is impossible to separate their mental
peculiarities in the way I have done: the tumbling of pigeons, which I
have instanced as a consensual movement, might be called a trick and is
associated with a taste for flying in a close flock at a great height.
Certain breeds of fowls have a taste for roosting in trees. The
different actions of pointers and setters might have been adduced in
the same class, as might the peculiar manner of hunting of
the spaniel. Even in the same breed of dogs, namely in fox-hounds, it
is the fixed opinion of those best able to judge that the different
pups are born with different tendencies; some are best to find their
fox in the cover; some are apt to run straggling, some are best to make
casts and to recover the lost scent, &c.; and that these
peculiarities undoubtedly are transmitted to their progeny. Or again
the tendency to point might be adduced as a distinct habit which has
become inherited,—as might the tendency of a true sheep dog (as I have
been assured is the case) to run round the flock instead of directly at
them, as is the case with other young dogs when attempted to be taught.
The "transandantes" sheep1in Spain, which for
some centuries have been yearly taken a journey of several hundred
miles from one province

to another, know when the time comes, and show the
greatest restlessness (like migratory birds in confinement), and are
prevented with difficulty from starting by themselves, which they
sometimes do, and find their own way. There is a case on good evidence1 of a sheep which, when she lambed, would return across a mountainous
country to her own birth-place, although at other times of year not of
a rambling disposition. Her lambs inherited this same disposition, and
would go to produce their young on the farm whence their parent came;
and so troublesome was this habit that the whole family was destroyed.

These facts must lead to the conviction, justly wonderful
as it is, that almost infinitely numerous shades of disposition, of
tastes, of peculiar movements, and even of individual actions, can be
modified or acquired by one individual and transmitted to its
offspring. One is forced to admit that mental phenomena (no doubt
through their intimate connection with the brain) can be inherited,
like infinitely numerous and fine differences of corporeal structure.
In the same manner as peculiarities of corporeal structure slowly
acquired or lost during mature life (especially cognisant <?> in
disease), as well as congenital peculiarities, are transmitted; so it
appears to be with the mind. The inherited paces in the horse have no
doubt been acquired by compulsion during the lives of the parents: and
temper and tameness may be modified in a breed by the treatment which
the individuals receive. Knowing that a pig has been taught to point,
one would suppose that this quality in pointer-dogs was the simple
result of habit, but some facts, with respect to the occasional
appearance of a similar quality in other dogs, would make one suspect
that it originally

1 In the margin "Hogg" occurs as
authority for this fact. For the reference, see p. 17, note 4.

appeared in a less perfect degree, "by chance,"
that is from a congenital tendency1 in the parent of the
breed of pointers. One cannot believe that the tumbling, and high
flight in a compact body, of one breed of pigeons has been taught; and
in the case of the slight differences in the manner of hunting in young
fox-hounds, they are doubtless congenital. The inheritance of the
foregoing and similar mental phenomena ought perhaps to create less
surprise, from the reflection that in no case do individual acts of
reasoning, or movements, or other phenomena connected with
consciousness, appear to be transmitted. An action, even a very
complicated one, when from long practice it is performed unconsciously
without any effort (and indeed in the case of many peculiarities of
manners opposed to the will) is said, according to a common expression,
to be performed "instinctively." Those cases of languages, and of
songs, learnt in early childhood and quite forgotten, being perfectly repeated during the unconsciousness of illness, appear to me only
a few degrees less wonderful than if they had been transmitted to a
second generation2.

Hereditary habits compared
with instincts.

The chief characteristics of true instincts appear to be
their invariability and non-improvement during the mature age of the
individual animal: the absence of knowledge of the end, for which the
action is performed, being associated, however, sometimes with a degree
of reason; being subject to mistakes and

1 In the Origin, Ed.
i., he speaks more decidedly against the belief that instincts are
hereditary habits, see for instance pp. 209, 214, Ed. vi. pp. 321, 327.
He allows, however, something to habit (p. 216).

2 A suggestion of Hering's and
S. Butler's views on memory and inheritance. It is not, however,
implied that Darwin was inclined to accept these opinions.

being associated with certain states of the body or times
of the year or day. In most of these respects there is a resemblance in
the above detailed cases of the mental qualities acquired or modified
during domestication. No doubt the instincts of wild animals are more
uniform than those habits or qualities modified or recently acquired
under domestication, in the same manner and from the same causes that
the corporeal structure in this state is less uniform than in beings in
their natural conditions. I have seen a young pointer point as fixedly,
the first day it was taken out, as any old dog; Magendie says this was
the case with a retriever which he himself reared: the tumbling of
pigeons is not probably improved by age: we have seen that in the case
above given that the young sheep inherited the migratory tendency to
their particular birth-place the first time they lambed. This last fact
offers an instance of a domestic instinct being associated with a state
of body; as do the "transandantes" sheep with a time of year.
Ordinarily the acquired instincts of domestic animals seem to require a
certain degree of education (as generally in pointers and retrievers)
to be perfectly developed: perhaps this holds good amongst wild animals
in rather a greater degree than is generally supposed; for instance, in
the singing of birds, and in the knowledge of proper herbs in
Ruminants. It seems pretty clear that bees transmit knowledge from
generation to generation. Lord Brougham1 insists strongly on
ignorance of the end proposed being eminently characteristic of true
instincts; and this appears to me to apply to many acquired hereditary
habits; for instance, in the case of the young pointer alluded to
before, which pointed so steadfastly the first day that we were obliged
several times to carry

him away1. This puppy not only pointed at
sheep, at large white stones, and at every little bird, but likewise
"backed" the other pointers: this young dog must have been as
unconscious for what end he was pointing, namely to facilitate his
master's killing game to eat, as is a butterfly which lays her eggs on
a cabbage, that her caterpillars would eat the leaves. So a horse that
ambles instinctively, manifestly is ignorant that he performs that
peculiar pace for the ease of man; and if man had never existed, he
would never have ambled. The young pointer pointing at white stones
appears to be as much a mistake of its acquired instinct, as in the
case of flesh-flies laying their eggs on certain flowers instead of
putrifying meat. However true the ignorance of the end may generally
be, one sees that instincts are associated with some degree of reason;
for instance, in the case of the tailor-bird, who spins threads with
which to make her nest <yet> will use artificial threads when she can
procure them2; so it has been known that an old pointer has
broken his point and gone round a hedge to drive out a bird towards his
master3.

There is one other quite distinct method by which the
instincts or habits acquired under domestication may be compared with
those given by nature, by a test of a fundamental kind; I mean the
comparison of the mental powers of mongrels and hybrids. Now the
instincts, or habits, tastes, and dispositions of one breed of
animals, when crossed with another breed, for instance a shepherd-

1 This case is more briefly
given in the Origin, Ed. i. p. 213, vi. p. 326. The simile of
the butterfly occurs there also.

3 In the margin is written
"Retriever killing one bird." This refers to the cases given in the Descent
of Man, 2nd Ed. (in 1 vol.) p. 78, of a retriever being puzzled
how to deal with a wounded and a dead bird, killed the former and
carried both at once. This was the only known instance of her wilfully
injuring game.

dog with a harrier, are blended and appear in the same
curiously mixed degree, both in the first and succeeding generations,
exactly as happens when one species is crossed with another1.
This would hardly be the case if there was any fundamental difference
between the domestic and natural instinct2; if the former
were, to use a metaphorical expression, merely superficial.

Variation in the mental
attributes of wild animals.

With respect to the variation3 of the mental
powers of animals in a wild state, we know that there is a considerable
difference in the disposition of different individuals of the same
species, as is recognised by all those who have had the charge of
animals in a menagerie. With respect to the wildness of animals, that
is fear directed particularly against man, which appears to be as true
an instinct as the dread of a young mouse of a cat, we have excellent
evidence that it is slowly acquired and becomes hereditary. It is also
certain that, in a natural state, individuals of the same species lose

1 See Origin, Ed. i.
p. 214, vi. p. 327.

2 <Note in original.> Give some
definition of instinct, or at least give chief attributes. <In Origin,
Ed. i. p. 207, vi. p. 319, Darwin refuses to define instinct.> The term
instinct is often used in <a> sense which implies no more than that the
animal does the action in question. Faculties and instincts may I think
be imperfectly separated. The mole has the faculty of scratching
burrows, and the instinct to apply it. The bird of passage has the
faculty of finding its way and the instinct to put it in action at
certain periods. It can hardly be said to have the faculty of knowing
the time, for it can possess no means, without indeed it be some
consciousness of passing sensations. Think over all habitual actions
and see whether faculties and instincts can be separated. We have
faculty of waking in the night, if an instinct prompted us to do
something at certain hour of night or day. Savages finding their way.
Wrangel's account—probably
a faculty inexplicable by the possessor. There are besides faculties "means,"
as conversion of larvae into neuters and queens. I think all this
generally implied, anyhow useful. <This discussion, which does not
occur in the Origin, is a first draft of that which follows
in the text, p. 123.>

3 A short discussion of a
similar kind occurs in the Origin, Ed. i. p. 211, vi. p. 324.

or do not practice their migratory instincts—as
woodcocks in Madeira. With respect to any variation in the more
complicated instincts, it is obviously most difficult to detect, even
more so than in the case of corporeal structure, of which it has been
admitted the variation is exceedingly small, and perhaps scarcely any
in the majority of species at any one period. Yet, to take one
excellent case of instinct, namely the nests of birds, those who have
paid most attention to the subject maintain that not only certain
individuals <? species> seem to be able to build very imperfectly, but
that a difference in skill may not unfrequently be detected between
individuals1. Certain birds, moreover, adapt their nests to
circumstances; the water-ouzel makes no vault when she builds under
cover of a rock—the sparrow
builds very differently when its nest is in a tree or in a hole, and
the golden-crested wren sometimes suspends its nest below and sometimes
places it on the branches of trees.

Principles of Selection
applicable to instincts.

As the instincts of a species are fully as important to
its preservation and multiplication as its corporeal structure, it is
evident that if there be the slightest congenital differences in the
instincts and habits, or if certain individuals during their lives are
induced or compelled to vary their habits, and if such differences are
in the smallest degree more favourable, under slightly modified
external conditions, to their preservation, such individuals must in
the long run have a better chance of being preserved and of
multiplying2. If this be admitted, a series of small changes
may, as in the case of corporeal structure, work great changes in the
mental powers, habits and instincts of any species.

1 This sentence agrees with the MS.,
but is clearly in need of correction.

Every one will at first be inclined to explain (as I did
for a long time) that many of the more complicated and wonderful
instincts could not be acquired in the manner here supposed1.
The Second Part of this work is devoted to the general consideration of
how far the general economy of nature justifies or opposes the belief
that related species and genera are descended from common stocks; but
we may here consider whether the instincts of animals offer such a primâ
facie case of impossibility of gradual acquirement, as to justify
the rejection of any such theory, however strongly it may be supported
by other facts. I beg to repeat that I wish here to consider not the probability but the possibility of complicated instincts having
been acquired by the slow and long-continued selection of very slight
(either congenital or produced by habit) modifications of foregoing
simpler instincts; each modification being as useful and necessary, to
the species practising it, as the most complicated kind.

First, to take the case of birds'-nests; of existing
species (almost infinitely few in comparison with the multitude which
must have existed, since the period of the new Red Sandstone of N.
America, of whose habits we must always remain ignorant) a tolerably
perfect series could be made from eggs

1 This discussion is interesting
in differing from the corresponding: section of the Origin,
Ed. i. p. 216, vi. p. 330, to the end of the chapter. In the present
Essay the subjects dealt with are nest-making instincts, including the
egg-hatching habit of the Australian bush-turkey. The power of
"shamming death." "Faculty" in relation to instinct. The instinct of
lapse of time, and of direction. Bees' cells very briefly given. Birds
feeding their young on food differing from their own natural food. In
the Origin, Ed. i., the cases discussed are the instinct of
laying eggs in other birds' nests; the slave-making instinct in ants;
the construction of the bee's comb, very fully discussed.

laid on the bare ground, to others with a few sticks just
laid round them, to a simple nest like the wood-pigeons, to others more
and more complicated: now if, as is asserted, there occasionally exist
slight differences in the building powers of an individual, and if,
which is at least probable, that such differences would tend to be
inherited, then we can see that it is at least possible that
the nidificatory instincts may have been acquired by the gradual
selection, during thousands and thousands of generations, of the eggs
and young of those individuals, whose nests were in some degree better
adapted to the preservation of their young, under the then existing
conditions. One of the most surprising instincts on record is that of
the Australian bush-turkey, whose eggs are hatched by the heat
generated from a huge pile of fermenting materials, which it heaps
together; but here the habits of an allied species show how this
instinct might possibly have been acquired. This second
species inhabits a tropical district, where the heat of the sun is
sufficient to hatch its eggs; this bird, burying its eggs, apparently
for concealment, under a lesser heap of rubbish, but of a dry nature,
so as not to ferment. Now suppose this bird to range slowly into a
climate which was cooler, and where leaves were more abundant, in that
case, those individuals, which chanced to have their collecting
instinct strongest developed, would make a somewhat larger pile, and
the eggs, aided during some colder season, under the slightly cooler
climate by the heat of incipient fermentation, would in the long run be
more freely hatched and would probably produce young ones with the same
more highly developed collecting tendencies; of these again, those with
the best developed powers would again tend to rear most young. Thus
this strange instinct might possibly be acquired, every
individual bird being

as ignorant of the laws of fermentation, and the
consequent development of heat, as we know they must be.

Secondly, to take the case of animals feigning death (as
it is commonly expressed) to escape danger. In the case of insects, a
perfect series can be shown, from some insects, which momentarily stand
still, to others which for a second slightly contract their legs, to
others which will remain immovably drawn together for a quarter of an
hour, and may be torn asunder or roasted at a slow fire, without
evincing the smallest sign of sensation. No one will doubt that the
length of time, during which each remains immovable, is well adapted to
<favour the insect's> escape <from> the dangers to which it is most
exposed, and few will deny the possibility of the change
from one degree to another, by the means and at the rate already
explained. Thinking it, however, wonderful (though not impossible) that
the attitude of death should have been acquired by methods which imply
no imitation, I compared several species, when feigning, as is said,
death, with others of the same species really dead, and their attitudes
were in no one case the same.

Thirdly, in considering many instincts it is useful to endeavour to separate the faculty1 by which they perform it, and
the mental power which urges to the performance, which is more properly
called an instinct. We have an instinct to eat, we have jaws &c. to
give us the faculty to do so. These faculties are often unknown to us:
bats, with their eyes destroyed, can avoid strings suspended across a
room, we know not at present by what faculty they do this. Thus also,
with migratory birds, it is a

1 The distinction between faculty and instinct corresponds in some degree to that between
perception of a stimulus and a specific reaction. I imagine that the
author would have said that the sensitiveness to light possessed by a
plant is faculty, while instinct decides whether
the plant curves to or from the source of illumination.

wonderful instinct which urges them at certain times of
the year to direct their course in certain directions, but it is a
faculty by which they know the time and find their way. With respect to
time1, man without seeing the sun can judge to a certain
extent of the hour, as must those cattle which come down from the
inland mountains to feed on sea-weed left bare at the changing hour of
low-water2. A hawk (D'Orbigny) seems certainly to have
acquired a knowledge of a period of every 21 days. In the cases already
given of the sheep which travelled to their birth-place to cast their
lambs, and the sheep in Spain which know their time of march3,
we may conjecture that the tendency to move is associated, we may then
call it instinctively, with some corporeal sensations. With respect to
direction we can easily conceive how a tendency to travel in a certain
course may possibly have been acquired, although we must remain
ignorant how birds are able to preserve any direction whatever in a
dark night over the wide ocean. I may observe that the power of some
savage races of mankind to find their way, although perhaps wholly
different from the faculty of birds, is nearly as unintelligible to us.
Bellinghausen, a skilful navigator, describes with the utmost wonder
the manner in which some Esquimaux guided him to a certain point, by a
course never straight, through newly formed hummocks of ice, on a thick
foggy day, when he with a compass found it impossible, from having no
landmarks, and from their course being so extremely crooked, to
preserve any sort of uniform

1 <Note in the original in an
unknown handwriting.> At the time when corn was pitched in the market
instead of sold by sample, the geese in the town fields of Newcastle
<Staffordshire?> used to know market day and come in to pick up the
corn spilt.

2 <Note in original.> Macculloch
and others.

3 I can find no reference to the transandantes sheep in Darwin's published work. He was
possibly led to doubt the accuracy of the statement on which he relied.
For the case of the sheep returning to their birth-place see p. 17,
note 4.

direction: so it is with Australian savages in thick
forests. In North and South America many birds slowly travel northward
and southward, urged on by the food they find, as the seasons change;
let them continue to do this, till, as in the case of the sheep in
Spain, it has become an urgent instinctive desire, and they will
gradually accelerate their journey. They would cross narrow rivers, and
if these were converted by subsidence into narrow estuaries, and
gradually during centuries to arms of the sea, still we may suppose
their restless desire of travelling onwards would impel them to cross
such an arm, even if it had become of great width beyond their span of
vision. How they are able to preserve a course in any direction, I have
said, is a faculty unknown to us. To give another illustration of the
means by which I conceive it possible that the direction of
migrations have been determined. Elk and reindeer in N. America
annually cross, as if they could marvellously smell or see at the
distance of a hundred miles, a wide tract of absolute desert, to arrive
at certain islands where there is a scanty supply of food; the changes
of temperature, which geology proclaims, render it probable that this
desert tract formerly supported some vegetation, and thus these
quadrupeds might have been annually led on, till they reached the more
fertile spots, and so acquired, like the sheep of Spain, their
migratory powers.

Fourthly, with respect to the combs of the hive-bee1;
here again we must look to some faculty or means by which they make
their hexagonal cells, without indeed we view these instincts as mere
machines. At present such a faculty is quite unknown: Mr Waterhouse
supposes that several bees are led by their instinct to excavate a mass
of wax to a certain thinness, and that the result of this

is that hexagons necessarily remain. Whether this or some
other theory be true, some such means they must possess. They abound,
however, with true instincts, which are the most wonderful that are
known. If we examine the little that is known concerning the habits of
other species of bees, we find much simpler instincts: the humble bee
merely fills rude balls of wax with honey and aggregates them together
with little order in a rough nest of grass. If we knew the instinct of
all the bees, which ever had existed, it is not improbable that we
should have instincts of every degree of complexity, from actions as
simple as a bird making a nest, and rearing her young, to the wonderful
architecture and government of the hive-bee; at least such is possible,
which is all that I am here considering.

Finally, I will briefly consider under the same point of
view one other class of instincts, which have often been advanced as
truly wonderful, namely parents bringing food to their young which they
themselves neither like nor partake of1;—for instance, the
common sparrow, a granivorous bird, feeding its young with
caterpillars. We might of course look into the case still earlier, and
seek how an instinct in the parent, of feeding its young at all, was
first derived; but it is useless to waste time in conjectures on a
series of gradations from the young feeding themselves and being
slightly and occasionally assisted in their search, to their entire
food being brought to them. With respect to the parent bringing a
different kind of food from its own kind, we may suppose either that
the remote stock, whence the sparrow and other congenerous birds have
descended, was insectivorous, and that its own habits and structure
have been changed, whilst its ancient instincts with respect to its
young have remained

1 This is an expansion of an
obscure passage in the Essay of 1842, p. 19.

unchanged; or we may suppose that the parents have been
induced to vary slightly the food of their young, by a slight scarcity
of the proper kind (or by the instincts of some individuals not being
so truly developed), and in this case those young which were most
capable of surviving were necessarily most often preserved, and would
themselves in time become parents, and would be similarly compelled to
alter their food for their young. In the case of those animals, the
young of which feed themselves, changes in their instincts for food,
and in their structure, might be selected from slight variations, just
as in mature animals. Again, where the food of the young depends on
where the mother places her eggs, as in the case of the caterpillars of
the cabbage-butterfly, we may suppose that the parent stock of the
species deposited her eggs sometimes on one kind and sometimes on
another of congenerous plants (as some species now do), and if the
cabbage suited the caterpillars better than any other plant, the
caterpillars of those butterflies, which had chosen the cabbage, would
be most plentifully reared, and would produce butterflies more apt to
lay their eggs on the cabbage than on the other congenerous plants.

However vague and unphilosophical these conjectures may
appear, they serve, I think, to show that one's first impulse utterly
to reject any theory whatever, implying a gradual acquirement of these
instincts, which for ages have excited man's admiration, may at least
be delayed. Once grant that dispositions, tastes, actions or habits can
be slightly modified, either by slight congenital differences (we must
suppose in the brain) or by the force of external circumstances, and
that such slight modifications can be rendered inheritable,—a
proposition which no one can reject,—and it will be difficult to put
any limit to the complexity and wonder of

Difficulties in the
acquirement by Selection of complex corporeal structures.

After the past discussion it will perhaps be convenient
here to consider whether any particular corporeal organs, or the entire
structure of any animals, are so wonderful as to justify the rejection primâ
facie of our theory1. In the case of the eye, as with
the more complicated instincts, no doubt one's first impulse is to
utterly reject every such theory. But if the eye from its most
complicated form can be shown to graduate into an exceedingly simple
state,—if selection can produce the smallest change, and if such a
series exists, then it is clear (for in this work we have nothing to do
with the first origin of organs in their simplest forms2)
that it may possibly have been acquired by gradual selection
of slight, but in each case, useful deviations3. Every
naturalist, when he meets with any new and singular organ, always
expects to find, and looks for, other and simpler modifications of it
in other beings. In the case of the eye, we have a multitude of
different forms, more or less simple, not graduating

1 The difficulties discussed in
the Origin, Ed. i. p. 171, vi. p. 207, are the rarity of
transitional varieties, the origin of the tail of the giraffe; the
otter-like polecat (Mustela vison); the flying habit of the
bat; the penguin and the logger-headed duck; flying fish; the
whale-like habit of the bear; the woodpecker; diving petrels; the eye;
the swimming bladder; Cirripedes; neuter insects; electric organs.

Of these, the polecat, the bat, the
woodpecker, the eye, the swimming bladder are discussed in the present
Essay, and in addition some botanical problems.

2 In the Origin, Ed.
vi. p. 275, the author replies to Mivart's criticisms (Genesis of
Species, 1871), referring especially to that writer's objection
"that natural selection is incompetent to account for the incipient
stages of useful structures."

3 <The following sentence seems
to have been intended for insertion here> "and that each eye throughout
the animal kingdom is not only most useful, but perfect for
its possessor."

into each other, but separated by sudden gaps or
intervals; but we must recollect how incomparably greater would the
multitude of visual structures be if we had the eyes of every fossil
which ever existed. We shall discuss the probable vast proportion of
the extinct to the recent in the succeeding Part. Notwithstanding the
large series of existing forms, it is most difficult even to conjecture
by what intermediate stages very many simple organs could possibly have
graduated into complex ones: but it should be here borne in mind, that
a part having originally a wholly different function, may on the theory
of gradual selection be slowly worked into quite another use; the
gradations of forms, from which naturalists believe in the hypothetical
metamorphosis of part of the ear into the swimming bladder in fishes1,
and in insects of legs into jaws, show the manner in which this is
possible. As under domestication, modifications of structure take
place, without any continued selection, which man finds very useful, or
valuable for curiosity (as the hooked calyx of the teazle, or the ruff
round some pigeons' necks), so in a state of nature some small
modifications, apparently beautifully adapted to certain ends, may
perhaps be produced from the accidents of the reproductive system, and
be at once propagated without long-continued selection of small
deviations towards that structure2. In conjecturing by what
stages any complicated organ in a species may have arrived at its
present state, although we may look to the analogous organs in other
existing species, we should do this merely to aid and guide our
imaginations; for to know the real stages we

1Origin, Ed. i. p.
190, vi. p. 230.

2 This is one of the most
definite statements in the present Essay of the possible importance of sports or what would now be called mutations. As is well known
the author afterwards doubted whether species could arise in this way.
See Origin, Ed. v. p. 103, vi. p. 110, also Life and
Letters, vol. iii. p. 107.

must look only through one line of species, to one ancient
stock, from which the species in question has descended. In considering
the eye of a quadruped, for instance, though we may look at the eye of
a molluscous animal or of an insect, as a proof how simple an organ
will serve some of the ends of vision; and at the eye of a fish as a
nearer guide of the manner of simplication; we must remember that it is
a mere chance (assuming for a moment the truth of our theory) if any
existing organic being has preserved any one organ, in exactly the same
condition, as it existed in the ancient species at remote geological
periods.

The nature or condition of certain structures has been
thought by some naturalists to be of no use to the possessor1,
but to have been formed wholly for the good of other species; thus
certain fruit and seeds have been thought to have been made nutritious
for certain animals—numbers
of insects, especially in their larval state, to exist for the same end—certain
fish to be bright coloured to aid certain birds of prey in catching
them, &c. Now could this be proved (which I am far from admitting)
the theory of natural selection would be quite overthrown; for it is
evident that selection depending on the advantage over others of one
individual with some slight deviation would never produce a structure
or quality profitable only to another species. No doubt one being takes
advantage of qualities in another, and may even cause its
extermination; but this is far from proving that this quality was
produced for such an end. It may be advantageous to a plant to have its
seeds attractive to animals, if one out of a hundred or a thousand
escapes being

1 See Origin, Ed. i.
p. 210, vi. p. 322, where the question is discussed for the case of
instincts with a proviso that the same argument applies to structure.
It is briefly stated in its general bearing in Origin, Ed. i.
p. 87, vi. p. 106.

digested, and thus aids dissemination: the bright colours
of a fish may be of some advantage to it, or more probably may result
from exposure to certain conditions in favourable haunts for food, notwithstanding it becomes subject to be caught more easily by certain birds.

If instead of looking, as above, at certain individual
organs, in order to speculate on the stages by which their parts have
been matured and selected, we consider an individual animal, we meet
with the same or greater difficulty, but which, I believe, as in the
case of single organs, rests entirely on our ignorance. It may be asked
by what intermediate forms could, for instance, a bat possibly have
passed; but the same question might have been asked with respect to the
seal, if we had not been familiar with the otter and other semi-aquatic
carnivorous quadrupeds. But in the case of the bat, who can say what
might have been the habits of some parent form with less developed
wings, when we now have insectivorous opossums and herbivorous
squirrels fitted for merely gliding through the air1. One
species of bat is at present partly aquatic in its habits2.
Woodpeckers and tree-frogs are especially adapted, as their names
express, for climbing trees; yet we have species of both inhabiting the
open plains of La Plata, where a tree does not exist3. I
might argue from this circumstance that a structure eminently fitted
for climbing trees might descend from forms inhabiting a country where
a tree

1 <Note in original.> No one
will dispute that the gliding is most useful, probably necessary for
the species in question.

2 <Note in original.> Is this
the Galeopithecus? I forget. <Galeopithecus "or the flying
Lemur" is mentioned in the corresponding discussion in the Origin,
Ed. i. p. 181, vi. p. 217, as formerly placed among the bats. I do not
know why it is described as partly aquatic in its habits.>

3 In the Origin, Ed.
vi. p. 221, the author modified the statement that it never climbs
trees; he also inserted a sentence quoting Mr Hudson to the effect that
in other districts this woodpecker climbs trees and bores holes. See Mr
Darwin's paper, Zoolog. Soc. Proc., 1870, and Life and
Letters, iii. p. 153.

did not exist. Notwithstanding these and a multitude of
other well-known facts, it has been maintained by several authors that
one species, for instance of the carnivorous order, could not pass into
another, for instance into an otter, because in its transitional state
its habits would not be adapted to any proper conditions of life; but
the jaguar1 is a thoroughly terrestrial quadruped in its
structure, yet it takes freely to the water and catches many fish; will
it be said that it is impossible that the conditions of its
country might become such that the jaguar should be driven to feed more
on fish than they now do; and in that case is it impossible, is it not
probable, that any the slightest deviation in its instincts, its form
of body, in the width of its feet, and in the extension of the skin
(which already unites the base of its toes) would give such individuals
a better chance of surviving and propagating young with
similar, barely perceptible (though thoroughly exercised), deviations2?
Who will say what could thus be effected in the course of ten thousand
generations? Who can answer the same question with respect to
instincts? If no one can, the possibility (for we are not in
this chapter considering the probability) of simple organs or
organic beings being modified by natural selection and the effects of
external agencies into complicated ones ought not to be absolutely
rejected.

ON THE EVIDENCE FAVOURABLE AND OPPOSED TO
THE VIEW THAT SPECIES ARE NATURALLY FORMED RACES, DESCENDED FROM COMMON
STOCKS

CHAPTER IV

ON THE NUMBER OF INTERMEDIATE FORMS
REQUIRED ON THE THEORY OF COMMON DESCENT; AND ON THEIR ABSENCE IN A
FOSSIL STATE

I must here premise that, according to the view ordinarily
received, the myriads of organisms, which have during past and present
times peopled this world, have been created by so many distinct acts of
creation. It is impossible to reason concerning the will of the
Creator, and therefore, according to this view, we can see no cause why
or why not the individual organism should have been created on any
fixed scheme. That all the organisms of this world have been produced
on a scheme is certain from their general affinities; and if this
scheme can be shown to be the same with that which would result from
allied organic beings descending from common stocks, it becomes highly
improbable that they have been separately created by individual acts of
the will of a Creator. For as well might it be said that, although the
planets move in courses conformably to the law of gravity, yet we ought
to

1 In the Origin the
division of the work into Parts I and II is omitted. In the MS.
the chapters of Part II are numbered afresh, the present being Ch. I of
Pt. II. I have thought it best to call it Ch. IV and there is evidence
that Darwin had some thought of doing the same. It corresponds to Ch.
IX of Origin, Ed. i., Ch. X in Ed. vi.

attribute the course of each planet to the individual act
of the will of the Creator1. It is in every case more
conformable with what we know of the government of this earth, that the
Creator should have imposed only general laws. As long as no method was
known by which races could become exquisitely adapted to various ends,
whilst the existence of species was thought to be proved by the
sterility2 of their offspring, it was allowable to
attribute each organism to an individual act of creation. But in the
two former chapters it has (I think) been shown that the production,
under existing conditions, of exquisitely adapted species, is at least possible. Is there then any direct evidence in favour <of> or against this
view? I believe that the geographical distribution of organic beings in
past and present times, the kind of affinity linking them together,
their so-called "metamorphic" and "abortive" organs, appear in favour
of this view. On the other hand, the imperfect evidence of the
continuousness of the organic series, which, we shall immediately see,
is required on our theory, is against it; and is the most weighty
objection3. The evidence, however, even on this point, as
far as it goes, is favourable; and considering the imperfection of our
knowledge, especially with respect to past ages, it would be surprising
if evidence drawn from such sources were not also imperfect.

As I suppose that species have been formed in

1 In the Essay of 1842 the
author uses astronomy in the same manner as an illustration. In the Origin this does not occur; the reference to the action of secondary
causes is more general, e.g. Ed. i. p. 488, vi. p. 668.

2 It is interesting to find the
argument from sterility given so prominent a place. In a corresponding
passage in the Origin, Ed. i. p. 480, vi. p. 659, it is more
summarily treated. The author gives, as the chief bar to the acceptance
of evolution, the fact that "we are always slow in admitting any great
change of which we do not see the intermediate steps"; and goes on to
quote Lyell on geological action. It will be remembered that the
question of sterility remained a difficulty for Huxley.

3 Similar statements occur in
the Essay of 1842, p. 24, note 1, and in the Origin, Ed. i.
p. 299.

an analogous manner with the varieties of the domesticated
animals and plants, so must there have existed intermediate forms
between all the species of the same group, not differing more than
recognised varieties differ. It must not be supposed necessary that
there should have existed forms exactly intermediate in character
between any two species of a genus, or even between any two varieties
of a species; but it is necessary that there should have existed every
intermediate form between the one species or variety of the common
parent, and likewise between the second species or variety, and this
same common parent. Thus it does not necessarily follow that there ever
has existed <a> series of intermediate sub-varieties (differing no more
than the occasional seedlings from the same seed-capsule, between
broccoli and common red cabbage; but it is certain that there has
existed, between broccoli and the wild parent cabbage, a series of such
intermediate seedlings, and again between red cabbage and the wild
parent cabbage: so that the broccoli and red cabbage are linked
together, but not necessarily by directly intermediate forms1.
It is of course possible that there may have been directly
intermediate forms, for the broccoli may have long since descended from
a common red cabbage, and this from the wild cabbage. So on my theory,
it must have been with species of the same genus. Still more must the
supposition be avoided that there has necessarily ever existed (though
one may have descended from <the> other) directly
intermediate forms between any two genera or families—for
instance between the genus Sus and the Tapir2;
although it is necessary that intermediate forms (not differing more
than the varieties

1 In the Origin, Ed.
i. p. 280, vi. p. 414 he uses his newly-acquired knowledge of pigeons
to illustrate this point.

of our domestic animals) should have existed between Sus
and some unknown parent form, and Tapir with this same parent form. The
latter may have differed more from Sus and Tapir than these two genera
now differ from each other. In this sense, according to our theory,
there has been a gradual passage (the steps not being wider apart than
our domestic varieties) between the species of the same genus, between
genera of the same family, and between families of the same order, and
so on, as far as facts, hereafter to be given, lead us; and the number
of forms which must have at former periods existed, thus to make good
this passage between different species, genera, and families, must have
been almost infinitely great.

What evidence1 is there of a number of
intermediate forms having existed, making a passage in the above sense,
between the species of the same groups? Some naturalists have supposed
that if every fossil which now lies entombed, together with all
existing species, were collected together, a perfect series in every
great class would be formed. Considering the enormous number of species
requisite to effect this, especially in the above sense of the forms
not being directly intermediate between the existing species
and genera, but only intermediate by being linked through a common but
often widely different ancestor, I think this supposition highly
improbable. I am however far from underrating the probable number of
fossilised species: no one who has attended to the wonderful progress
of palæontology during the last few years will doubt that we as yet
have found only an exceedingly small fraction of the species buried in
the crust of the earth. Although the almost infinitely numerous
intermediate forms in no one

class may have been preserved, it does not follow that
they have not existed. The fossils which have been discovered, it is
important to remark, do tend, the little way they go, to make good the
series; for as observed by Buckland they all fall into or between
existing groups1. Moreover, those that fall between our
existing groups, fall in, according to the manner required by our
theory, for they do not directly connect two existing species of
different groups, but they connect the groups themselves: thus the
Pachydermata and Ruminantia are now separated by several characters,
<for instance> the Pachydermata2 have both a tibia and
fibula, whilst Ruminantia have only a tibia; now the fossil
Macrauchenia has a leg bone exactly intermediate in this respect, and
likewise has some other intermediate characters. But the Macrauchenia
does not connect any one species of Pachydermata with some one other of
Ruminantia but it shows that these two groups have at one time been
less widely divided. So have fish and reptiles been at one time more
closely connected in some points than they now are. Generally in those
groups in which there has been most change, the more ancient the
fossil, if not identical with recent, the more often it falls between
existing groups, or into small existing groups which now lie between
other large existing groups. Cases like the foregoing, of which there
are many, form steps, though few and far between, in a series of the
kind required by my theory.

As I have admitted the high improbability, that if every
fossil were disinterred, they would compose in each of the Divisions of
Nature a perfect

1Origin, Ed. i. p.
329, vi. p. 471.

2 The structure of the Pachyderm
leg was a favourite with the author. It is discussed in the Essay of
1842, p. 48. In the present Essay the following sentence in the margin
appears to refer to Pachyderms and Ruminants: "There can be no doubt,
if we banish all fossils, existing groups stand more separate." The
following occurs between the lines "The earliest forms would be such as
others could radiate from."

series of the kind required; consequently I freely admit,
that if those geologists are in the right who consider the lowest known
formation as contemporaneous with the first appearances of life1;
or the several formations as at all closely consecutive; or any one
formation as containing a nearly perfect record of the organisms which
existed during the whole period of its deposition in that quarter of
the globe;—if such propositions are to be accepted, my theory must be
abandoned.

If the Palæozoic system is really contemporaneous with the
first appearance of life, my theory must be abandoned, both inasmuch as
it limits from shortness of time the total number of forms
which can have existed on this world, and because the organisms, as
fish, mollusca2 and star-fish found in its lower beds,
cannot be considered as the parent forms of all the successive species
in these classes. But no one has yet overturned the arguments of Hutton
and Lyell, that the lowest formations known to us are only those which
have escaped being metamorphosed <illegible>; if we argued from some
considerable districts, we might have supposed that even the Cretaceous
system was that in which life first appeared. From the number of
distant points, however, in which the Silurian system has been found to
be the lowest, and not always metamorphosed, there are some objections
to Hutton's and Lyell's view; but we must not forget that the now
existing land forms only 1/5 part of the superficies of the globe, and that this fraction is only
imperfectly known. With respect to the fewness of the organisms found
in the Silurian and other Palæozoic formations, there is less
difficulty, inasmuch as

1Origin, Ed. i. p.
307, vi. p. 448.

2 <Pencil insertion by the
author.> The parent-forms of Mollusca would probably differ greatly
from all recent,—it is not directly that any one division of Mollusca
would descend from first time unaltered, whilst others had become
metamorphosed from it.

(besides their gradual obliteration) we can expect
formations of this vast antiquity to escape entire denudation, only
when they have been accumulated over a wide area, and have been
subsequently protected by vast superimposed deposits: now this could
generally only hold good with deposits accumulating in a wide and deep
ocean, and therefore unfavourable to the presence of many living
things. A mere narrow and not very thick strip of matter, deposited
along a coast where organisms most abound, would have no chance of
escaping denudation and being preserved to the present time from such
immensely distant ages1.

If the several known formations are at all nearly
consecutive in time, and preserve a fair record of the organisms which
have existed, my theory must be abandoned. But when we consider the
great changes in mineralogical nature and texture between successive
formations, what vast and entire changes in the geography of the
surrounding countries must generally have been effected, thus wholly to
have changed the nature of the deposits on the same area. What time
such changes must have required! Moreover how often has it not been
found, that between two conformable and apparently immediately
successive deposits a vast pile of water-worn matter is interpolated in
an adjoining district. We have no means of conjecturing in many cases
how long a period2 has elapsed between successive
formations, for the species are often wholly different: as remarked by
Lyell, in some cases probably as long a period has elapsed between two
formations as the whole Tertiary system, itself broken by wide gaps.

Consult the writings of any one who has particularly
attended to any one stage in the Tertiary

1Origin, Ed. i. p.
291, vi. p. 426.

2 <Note in original.> Reflect on
coming in of the Chalk, extending from Iceland to the Crimea.

system (and indeed of every system) and see how deeply
impressed he is with the time required for its accumulation1.
Reflect on the years elapsed in many cases, since the latest beds
containing only living species have been formed;—see what Jordan Smith
says of the 20,000 years since the last bed, which is above the boulder
formation in Scotland, has been upraised; or of the far longer period
since the recent beds of Sweden have been upraised 400 feet, what an
enormous period the boulder formation must have required, and yet how
insignificant are the records (although there has been plenty of
elevation to bring up submarine deposits) of the shells, which we know
existed at that time. Think, then, over the entire length of the
Tertiary epoch, and think over the probable length of the intervals,
separating the Secondary deposits. Of these deposits, moreover, those
consisting of sand and pebbles have seldom been favourable, either to
the embedment or to the preservation of fossils2.

Nor can it be admitted as probable that any one Secondary
formation contains a fair record even of those organisms which are most
easily preserved, namely hard marine bodies. In how many cases have we
not certain evidence that between the deposition of apparently closely
consecutive beds, the lower one existed for an unknown time as land,
covered with trees. Some of the Secondary formations which contain most
marine remains appear to have been formed in a wide and not deep sea,
and therefore only those marine animals which live in such situations
would be preserved3. In all cases, on indented rocky coasts,
or any other coast, where sediment is not accumulating, although often
highly

1Origin, Ed. i. p.
282, vi. p. 416.

2Origin, Ed. i. pp.
288, 300, vi. pp. 422, 438.

3 <Note in original.> Neither
highest or lowest fish (i.e. Myxina <?> or Lepidosiren) could
be preserved in intelligible condition in fossils.

favourable to marine animals, none can be embedded: where
pure sand and pebbles are accumulating few or none will be preserved. I
may here instance the great western line of the S. American coast1,
tenanted by many peculiar animals, of which none probably will be
preserved to a distant epoch. From these causes, and especially from
such deposits as are formed along a line of coast, steep above and
below water, being necessarily of little width, and therefore more
likely to be subsequently denuded and worn away, we can see why it is
improbable that our Secondary deposits contain a fair record of the
Marine Fauna of any one period. The East Indian Archipelago offers an
area, as large as most of our Secondary deposits, in which there are
wide and shallow seas, teeming with marine animals and in which
sediment is accumulating; now supposing that all the hard marine
animals, or rather those having hard parts to preserve, were preserved
to a future age, excepting those which lived on rocky shores where no
sediment or only sand and gravel were accumulating, and excepting those
embedded along the steeper coasts, where only a narrow fringe of
sediment was accumulating, supposing all this, how poor a notion would
a person at a future age have of the Marine Fauna of the present day.
Lyell2 has compared the geological series to a work of which
only the few latter but not consecutive chapters have been preserved;
and out of which, it may be added, very many leaves have been torn, the
remaining ones only illustrating a scanty portion of the Fauna of each
period. On

1Origin, Ed. i. p.
290, vi. p. 425.

2 See Origin, Ed. i.
p. 310, vi. p. 452 for Lyell's metaphor. I am indebted to Prof. Judd
for pointing out that Darwin's version of the metaphor is founded on
the first edition of Lyell's Principles, vol. I.
and vol. III.; see the Essay of 1842, p. 27.

this view, the records of anteceding ages confirm my
theory; on any other they destroy it.

Finally, if we narrow the question into, why do we not
find in some instances every intermediate form between any two species?
the answer may well be that the average duration of each specific form
(as we have good reason to believe) is immense in years, and that the
transition could, according to my theory, be effected only by
numberless small gradations; and therefore that we should require for
this end a most perfect record, which the foregoing reasoning teaches
us not to expect. It might be thought that in a vertical section of
great thickness in the same formation some of the species ought to be
found to vary in the upper and lower parts1, but it may be
doubted whether any formation has gone on accumulating without any
break for a period as long as the duration of a species; and if it had
done so, we should require a series of specimens from every part. How
rare must be the chance of sediment accumulating for some 20 or 30
thousand years on the same spot2, with the bottom subsiding,
so that a proper depth might be preserved for any one species to
continue living: what an amount of subsidence would be thus required,
and this subsidence must not destroy the source whence the sediment
continued to be derived. In the case of terrestrial animals, what
chance is there when the present time is become a pleistocene formation
(at an earlier period than this, sufficient elevation to expose marine
beds could not be expected), what chance is there that future
geologists will make out the innumerable transitional sub-varieties,
through which the short-horned and long-

1 See More Letters, vol. I. pp. 344-7, for Darwin's interest in the celebrated
observations of Hilgendorf and Hyatt.

horned cattle (so different in shape of body) have been
derived from the same parent stock1? Yet this transition has
been effected in the same country, and in a far shorter
time, than would be probable in a wild state, both contingencies
highly favourable for the future hypothetical geologists being enabled
to trace the variation.

IN the Tertiary system, in the last uplifted beds, we find
all the species recent and living in the immediate vicinity; in rather
older beds we find only recent species, but some not living in the
immediate vicinity2; we then find beds with two or three or
a few more extinct or very rare species; then considerably more extinct
species, but with gaps in the regular increase; and finally we have
beds with only two or three or not one living species. Most geologists
believe that the gaps in the percentage, that is the sudden increments,
in the number of the extinct species in the stages of the Tertiary
system are due to the imperfection of the geological record. Hence we
are led to believe that the species in the Tertiary system have been
gradually introduced; and from analogy to carry on the same view to the
Secondary formations. In these latter, however, entire groups of
species generally come in abruptly; but this would naturally result,
if, as argued in the foregoing chapter, these Secondary deposits are
separated by wide epochs. Moreover it is important to observe that,
with our increase of knowledge, the gaps between the older formations
become fewer and smaller; geologists of

a few years standing remember how beautifully has the
Devonian system1 come in between the Carboniferous and
Silurian formations. I need hardly observe that the slow and gradual
appearance of new forms follows from our theory, for to form a new
species, an old one must not only be plastic in its organization,
becoming so probably from changes in the conditions of its existence,
but a place in the natural economy of the district must [be made,] come
to exist, for the selection of some new modification of its structure,
better fitted to the surrounding conditions than are the other
individuals of the same or other species2.

In the Tertiary system the same facts, which make us admit
as probable that new species have slowly appeared, lead to the
admission that old ones have slowly disappeared, not several together,
but one after another; and by analogy one is induced to extend this
belief to the Secondary and Palæozoic epochs. In some cases, as the
subsidence of a flat country, or the breaking or the joining of an
isthmus, and the sudden inroad of many new and destructive species,
extinction might be locally sudden. The view entertained by many
geologists, that each fauna of each Secondary epoch has been suddenly
destroyed over the whole world, so that no succession could be left for
the production of new forms, is subversive of my theory, but I see no
grounds whatever to admit such a view. On the

1 In the margin the author has
written "Lonsdale." This refers to W. Lonsdale's paper "Notes on the
age of the Limestone of South Devonshire," Geolog. Soc. Trans., Series
2, vol. V. 1840, p. 721. According to Mr H. B. Woodward
(History
of the Geological Society of London, 1907, p. 107) "Lonsdale's
'important and original suggestion of the existence of an intermediary
type of Palæozoic fossils, since called Devonian,' led to a change
which was then 'the greatest ever made at one time in the
classification of our English formations '." Mr Woodward's quotations
are from Murchison and Buckland.

2 <Note in original.> Better
begin with this. If species really, after catastrophes, created in
showers over world, my theory false. <In the above passage the author
is obviously close to his theory of divergence.>

contrary, the law, which has been made out, with reference
to distinct epochs, by independent observers, namely, that the wider
the geographical range of a species the longer is its duration in time,
seems entirely opposed to any universal extermination1. The
fact of species of mammiferous animals and fish being renewed at a
quicker rate than mollusca, though both aquatic; and of these the
terrestrial genera being renewed quicker than the marine; and the
marine mollusca being again renewed quicker than the Infusorial
animalcula, all seem to show that the extinction and renewal of species
does not depend on general catastrophes, but on the particular
relations of the several classes to the conditions to which they are
exposed2.

Some authors seem to consider the fact of a few species
having survived3 amidst a number of extinct forms (as is the
case with a tortoise and a crocodile out of the vast number of extinct
sub-Himalayan fossils) as strongly opposed to the view of species being
mutable. No doubt this would be the case, if it were presupposed with
Lamarck that there was some inherent tendency to change and development
in all species, for which supposition I see no evidence. As we see some
species at present adapted to a wide range of conditions, so we may
suppose that such species would survive unchanged and unexterminated
for a long time; time generally being from geological causes a
correlative of changing conditions. How at present one species becomes
adapted to a wide range, and another species to a restricted range of
conditions, is of difficult explanation.

1 Opposite to this passage the
author has written "d'Archiac, Forbes, Lyell."

2 This passage, for which the
author gives as authorities the names of Lyell, Forbes and Ehrenberg,
corresponds in part to the discussion beginning on p. 313 of Origin,
Ed. i, vi. p. 454.

The extinction of the larger quadrupeds, of which we
imagine we better know the conditions of existence, has been thought
little less wonderful than the appearance of new species; and has, I
think, chiefly led to the belief of universal catastrophes. When
considering the wonderful disappearance within a late period, whilst
recent shells were living, of the numerous great and small mammifers of
S. America, one is strongly induced to join with the catastrophists. I
believe, however, that very erroneous views are held on this subject.
As far as is historically known, the disappearance of species from any
one country has been slow—the
species becoming rarer and rarer, locally extinct, and finally lost1. It may be objected that this has been effected by man's direct
agency, or by his indirect agency in altering the state of the country;
in this latter case, however, it would be difficult to draw any just
distinction between his agency and natural agencies. But we now know in
the later Tertiary deposits, that shells become rarer and rarer in the
successive beds, and finally disappear: it has happened, also, that
shells common in a fossil state, and thought to have been extinct, have
been found to be still living species, but very rare ones 2.
If the rule is that organisms become extinct by becoming rarer and
rarer, we ought not to view their extinction, even in the case of the
larger quadrupeds, as anything wonderful and out of the common course
of events. For no naturalist thinks it wonderful that one species of a
genus should be rare and another abundant, notwithstanding he be

quite incapable of explaining the causes of the
comparative rareness1. Why is one species of willow-wren or
hawk or woodpecker common in England, and another extremely rare: why
at the Cape of Good Hope is one species of rhinoceros or antelope far
more abundant than other species? Why again is the same species much
more abundant in one district of a country than in another district? No
doubt there are in each case good causes: but they are unknown and
unperceived by us. May we not then safely infer that as certain causes
are acting unperceived around us, and are making one species
to be common and another exceedingly rare, that they might equally well
cause the final extinction of some species without being perceived by
us? We should always bear in mind that there is a recurrent struggle
for life in every organism, and that in every country a destroying
agency is always counteracting the geometrical tendency to increase in
every species; and yet without our being able to tell with certainty at
what period of life, or at what period of the year, the destruction
falls the heaviest. Ought we then to expect to trace the steps by which
this destroying power, always at work and scarcely perceived by us,
becomes increased, and yet if it continues to increase ever so slowly
(without the fertility of the species in question be likewise
increased) the average number of the individuals of that species must
decrease, and become finally lost. I may give a single instance of a
check causing local extermination which might long have escaped
discovery2; the horse, though swarming in a wild state in La
Plata, and likewise under apparently the most unfavourable conditions
in the scorched and alternately flooded plains of Caraccas, will not in
a wild

1 This point, on which the
author laid much stress, is discussed in the Origin, Ed. i.
p. 319, vi. p. 461.

state extend beyond a certain degree of latitude into the
intermediate country of Paraguay; this is owing to a certain fly
depositing its eggs on the navels of the foals: as, however, man with a little care can rear horses in a tame state abundantly in
Paraguay, the problem of its extinction is probably complicated by the
greater exposure of the wild horse to occasional famine from the
droughts, to the attacks of the jaguar and other such evils. In the
Falkland Islands the check to the increase of the wild horse
is said to be loss of the sucking foals1, from the stallions
compelling the mares to travel across bogs and rocks in search of food:
if the pasture on these islands decreased a little, the horse, perhaps,
would cease to exist in a wild state, not from the absolute want of
food, but from the impatience of the stallions urging the mares to
travel whilst the foals were too young.

From our more intimate acquaintance with domestic animals,
we cannot conceive their extinction without some glaring agency; we
forget that they would undoubtedly in a state of nature (where other
animals are ready to fill up their place) be acted on in some part of
their lives by a destroying agency, keeping their numbers on an average
constant. If the common ox was known only as a wild S. African species,
we should feel no surprise at hearing that it was a very rare species;
and this rarity would be a stage towards its extinction. Even in man,
so infinitely better known than any other inhabitant of this world, how
impossible it has been found, without statistical calculations, to
judge of the proportions of births and deaths, of the duration of life,
and of the increase and decrease of population; and still less of the
causes of such changes: and yet, as has so often been repeated,
decrease in

numbers or rarity seems to be the high-road to extinction.
To marvel at the extermination of a species appears to me to be the
same thing as to know that illness is the road to death,—to look at
illness as an ordinary event, nevertheless to conclude, when the sick
man dies, that his death has been caused by some unknown and violent
agency1.

In a future part of this work we shall show that, as a
general rule, groups of allied species2 gradually appear and
disappear, one after the other, on the face of the earth, like the
individuals of the same species: and we shall then endeavour to show
the probable cause of this remarkable fact.

ON THE GEOGRAPHICAL DISTRIBUTION OF ORGANIC
BEINGS IN PAST AND PRESENT TIMES

FOR convenience sake I shall divide this chapter into
three sections1. In the first place I shall endeavour to
state the laws of the distribution of existing beings, as far as our
present object is concerned; in the second, that of extinct; and in the
third section I shall consider how far these laws accord with the
theory of allied species having a common descent.

SECTION FIRST.

Distribution of the
inhabitants in the different continents.

In the following discussion I shall chiefly refer to
terrestrial mammifers, inasmuch as they are better known; their
differences in different countries, strongly marked; and especially as
the necessary

1 Chapters XI and XII in the Origin,
Ed. i., vi. chs. XII and XIII ("On geographical distribution") show
signs of having been originally one, in the fact that one summary
serves for both. The geological element is not separately treated
there, nor is there a separate section on "how far these laws accord
with the theory, &c."

In the MS. the author has
here written in the margin "If same species appear at two spot at once,
fatal to my theory." See Origin, Ed. i. p. 352, vi. p. 499

means of their transport are more evident, and confusion,
from the accidental conveyance by man of a species from one district to
another district, is less likely to arise. It is known that all
mammifers (as well as all other organisms) are united in one great
system; but that the different species, genera, or families of the same
order inhabit different quarters of the globe. If we divide the land1 into two divisions, according to the amount of difference, and
disregarding the numbers of the terrestrial mammifers inhabiting them,
we shall have first Australia including New Guinea; and secondly the
rest of the world: if we make a three-fold division, we shall have
Australia, S. America, and the rest of the world; I must observe that
North America is in some respects neutral land, from possessing some S.
American forms, but I believe it is more closely allied (as it
certainly is in its birds, plants and shells) with Europe. If our
division had been fourfold, we should have had Australia, S. America,
Madagascar (though inhabited by few mammifers) and the remaining land:
if five-fold, Africa, especially the southern eastern parts, would have
to be separated from the remainder of the world. These differences in
the mammiferous inhabitants of the several main divisions of the globe
cannot, it is well known, be explained by corresponding differences in
their conditions2; how similar are parts of tropical America
and Africa; and accordingly we find some analogous resemblances,—thus
both have monkeys, both large feline animals, both large Lepidoptera,
and large dung-feeding beetles; both have palms and epiphytes; and yet
the essential difference between their productions is as great as
between those of the arid plains of the Cape of Good Hope

1 This division of the land into
regions does not occur in the Origin, Ed. i.

and the grass-covered savannahs of La Plata1.
Consider the distribution of the Marsupialia, which are eminently
characteristic of Australia, and in a lesser degree of S. America; when
we reflect that animals of this division, feeding both on animal and
vegetable matter, frequent the dry open or wooded plains and mountains
of Australia, the humid impenetrable forests of New Guinea and Brazil;
the dry rocky mountains of Chile, and the grassy plains of Banda
Oriental, we must look to some other cause, than the nature of the
country, for their absence in Africa and other quarters of the world.

Furthermore it may be observed that all the
organisms inhabiting any country are not perfectly adapted to it2;
I mean by not being perfectly adapted, only that some few other
organisms can generally be found better adapted to the country than
some of the aborigines. We must admit this when we consider the
enormous number of horses and cattle which have run wild during the
three last centuries in the uninhabited parts of St Domingo, Cuba, and
S. America; for these animals must have supplanted some aboriginal
ones. I might also adduce the same fact in Australia, but perhaps it
will be objected that 30 or 40 years has not been a sufficient period
to test this power of struggling <with> and overcoming the aborigines.
We know the European mouse is driving before it that of New Zealand,
like the Norway rat has driven before it the old English species in
England. Scarcely an island can be named, where casually introduced
plants have not supplanted some of the native species: in La Plata the
Cardoon covers square leagues of country on

1 Opposite this passage is
written "not botanically" in Sir J. D. Hooker's hand. The
word palms is underlined three times and followed by three
exclamation marks. An explanatory note is added in the margin "singular
paucity of palms and epiphytes in Trop. Africa compared with Trop.
America and Ind. Or." <= East Indies>.

which some S. American plants must once have grown: the
commonest weed over the whole of India is an introduced Mexican poppy.
The geologist who knows that slow changes are in progress, replacing
land and water, will easily perceive that even if all the organisms of
any country had originally been the best adapted to it, this could
hardly continue so during succeeding ages without either extermination,
or changes, first in the relative proportional numbers of the
inhabitants of the country, and finally in their constitutions and
structure.

Inspection of a map of the world at once shows that the
five divisions, separated according to the greatest amount of
difference in the mammifers inhabiting them, are likewise those most
widely separated from each other by barriers1 which
mammifers cannot pass: thus Australia is separated from New Guinea and
some small adjoining islets only by a narrow and shallow strait;
whereas New Guinea and its adjoining islets are cut off from the other
East Indian islands by deep water. These latter islands, I may remark,
which fall into the great Asiatic group, are separated from each other
and the continent only by shallow water; and where this is the case we
may suppose, from geological oscillations of level, that generally
there has been recent union. South America, including the southern part
of Mexico, is cut off from North America by the West Indies, and the
great tableland of Mexico, except by a mere fringe of tropical forests
along the coast: it is owing, perhaps, to this fringe that N. America
possesses some S. American forms. Madagascar is entirely isolated.
Africa is also to a great extent isolated, although it approaches, by
many promontories and by lines of shallower sea, to Europe and Asia:
southern Africa, which is

1 On the general importance of
barriers, see Origin, Ed. i. p. 347, vi. p. 494.

the most distinct in its mammiferous inhabitants, is
separated from the northern portion by the Great Sahara Desert and the
table-land of Abyssinia. That the distribution of organisms is related
to barriers, stopping their progress, we clearly see by comparing the
distribution of marine and terrestrial productions. The marine animals
being different on the two sides of land tenanted by the same
terrestrial animals, thus the shells are wholly different on the
opposite sides of the temperate parts of South America1, as
they are (?) in the Red Sea and the Mediterranean. We can at once
perceive that the destruction of a barrier would permit two
geographical groups of organisms to fuse and blend into one. But the
original cause of groups being different on opposite sides of a barrier
can only be understood on the hypothesis of each organism having been
created or produced on one spot or area, and afterwards migrating as
widely as its means of transport and subsistence permitted it.

Relation of range in
genera and species.

It is generally2 found, that where a genus or
group ranges over nearly the entire world, many of the species
composing the group have wide ranges: on the other hand, where a group
is restricted to any one country, the species composing it generally
have restricted ranges in that country3. Thus among
mammifers the feline and canine genera are widely distributed, and many
of the individual species have enormous ranges [the genus Mus I
believe, however, is a strong exception to the rule].

1Origin, Ed. i. p.
348, vi. p. 495.

2 <Note in original.> The same
laws seem to govern distribution of species and genera, and individuals
in time and space. <See Origin, Ed. i. p. 350, vi. p. 497,
also a passage in the last chapter, p. 146.>

Mr Gould informs me that the rule holds with birds, as in
the owl genus, which is mundane, and many of the species range widely.
The rule holds also with land and fresh-water mollusca, with
butterflies and very generally with plants. As instances of the
converse rule, I may give that division of the monkeys which is
confined to S. America, and amongst plants, the Cacti, confined to the
same continent, the species of both of which have generally narrow
ranges. On the ordinary theory of the separate creation of each
species, the cause of these relations is not obvious; we can see no
reason, because many allied species have been created in the several
main divisions of the world, that several of these species should have
wide ranges; and on the other hand, that species of the same group
should have narrow ranges if all have been created in one main division
of the world. As the result of such and probably many other unknown
relations, it is found that, even in the same great classes of beings,
the different divisions of the world are characterised by either merely
different species, or genera, or even families: thus in cats, mice,
foxes, S. America differs from Asia and Africa only in species; in her
pigs, camels and monkeys the difference is generic or greater. Again,
whilst southern Africa and Australia differ more widely in their
mammalia than do Africa and S. America, they are more closely (though
indeed very distantly) allied in their plants.

Distribution of the
inhabitants in the same continent.

If we now look at the distribution of the organisms in any
one of the above main divisions of the world, we shall find it split up
into many regions, with all or nearly all their species distinct, but
yet

partaking of one common character. This similarity of type
in the subdivisions of a great region is equally well-known with the
dissimilarity of the inhabitants of the several great regions; but it
has been less often insisted on, though more worthy of remark. Thus for
instance, if in Africa or S. America, we go from south to north1,
or from lowland to upland, or from a humid to a dryer part, we find
wholly different species of those genera or groups which characterise
the continent over which we are passing. In these subdivisions we may
clearly observe, as in the main divisions of the world, that
sub-barriers divide different groups of species, although the opposite
sides of such sub-barriers may possess nearly the same climate, and may
be in other respects nearly similar: thus it is on the opposite sides
of the Cordillera of Chile, and in a lesser degree on the opposite
sides of the Rocky mountains. Deserts, arms of the sea, and even rivers
form the barriers; mere preoccupied space seems sufficient in several
cases: thus Eastern and Western Australia, in the same latitude, with
very similar climate and soils, have scarcely a plant, and few animals
or birds, in common, although all belong to the peculiar genera
characterising Australia. It is in short impossible to explain the
differences in the inhabitants, either of the main divisions of the
world, or of these sub-divisions, by the differences in their physical
conditions, and by the adaptation of their inhabitants. Some other
cause must intervene.

We can see that the destruction of sub-barriers would
cause (as before remarked in the case of the main divisions) two
sub-divisions to blend into one; and we can only suppose that the
original difference in the species, on the opposite sides of
sub-barriers, is due to the creation or production of

species in distinct areas, from which they have wandered
till arrested by such sub-barriers. Although thus far is pretty clear,
it may be asked, why, when species in the same main division of the
world were produced on opposite sides of a sub-barrier, both when
exposed to similar conditions and when exposed to widely different
influences (as on alpine and lowland tracts, as on arid and humid
soils, as in cold and hot climates), have they invariably been formed
on a similar type, and that type confined to this one division of the
world? Why when an ostrich1 was produced in the southern
parts of America, was it formed on the American type, instead of on the
African or on Australian types? Why when hare-like and rabbit-like
animals were formed to live on the Savannahs of La Plata, were they
produced on the peculiar Rodent type of S. America, instead of on the
true2 hare-type of North America, Asia and Africa? Why when
borrowing Rodents, and camel-like animals were formed to tenant the
Cordillera, were they formed on the same type3 with their
representatives on the plains? Why were the mice, and many birds of
different species on the opposite sides of the Cordillera, but exposed
to a very similar climate and soil, created on the same peculiar S.
American type? Why were the plants in Eastern and Western Australia,
though wholly different as species, formed on the same peculiar
Australian types? The generality of the rule, in so many places and
under such different circumstances, makes it highly remarkable and
seems to demand some explanation.

If we now look to the character of the inhabitants of
small islands1, we shall find that those situated close to
other land have a similar fauna with that land2, whilst
those at a considerable distance from other land often possess an
almost entirely peculiar fauna. The Galapagos Archipelago3 is a remarkable instance of this latter fact; here almost every bird,
its one mammifer, its reptiles, land and sea shells, and even fish, are
almost all peculiar and distinct species, not found in any other
quarter of the world: so are the majority of its plants. But although
situated at the distance of between 500 and 600 miles from the S.
American coast, it is impossible to even glance at a large part of its
fauna, especially at the birds, without at once seeing that they belong
to the American type4. Hence, in fact, groups of islands
thus circumstanced form merely small but well-defined sub-divisions of
the larger geographical divisions. But the fact is in such cases far
more striking: for taking the Galapagos Archipelago as an instance; in
the first place we must feel convinced, seeing that every island is
wholly volcanic and bristles with craters, that in a geological sense
the whole is of recent origin comparatively with a continent; and as
the species are nearly all peculiar, we must conclude that they have in
the same sense recently been produced on this very spot; and

2 This is an illustration of
the general theory of barriers (Origin, Ed. i. p. 347, vi. p.
494). At i. p. 391, vi. p. 544 the question is discussed from the point
of view of means of transport. Between the lines, above the words "with
that land," the author wrote "Cause, formerly joined, no one doubts
after Lyell."

although in the nature of the soil, and in a lesser degree
in the climate, there is a wide difference with the nearer part of the
S. American coast, we see that the inhabitants have been formed on the
same closely allied type. On the other hand, these islands, as far as
their physical conditions are concerned, resemble closely the Cape de
Verde volcanic group, and yet how wholly unlike are the productions of
these two archipelagoes. The Cape de Verde1 group, to which
may be added the Canary Islands, are allied in their inhabitants (of
which many are peculiar species) to the coast of Africa and southern
Europe, in precisely the same manner as the Galapagos Archipelago is
allied to America. We here clearly see that mere geographical proximity
affects, more than any relation of adaptation, the character of
species. How many islands in the Pacific exist far more like in their
physical conditions to Juan Fernandez than this island is to the coast
of Chile, distant 300 miles; why then, except from mere proximity,
should this island alone be tenanted by two very peculiar species of
humming-birds—that form of
birds which is so exclusively American?
Innumerable other similar cases might be adduced.

The Galapagos
Archipelago offers another, even more remarkable, example of the class
of facts we are here considering. Most of its genera are, as we have
said, American, many of them are mundane, or found everywhere, and some
are quite or nearly confined to this archipelago. The islands are of
absolutely similar composition, and exposed to the same climate; most
of them are in sight of each other; and yet several of the islands are
inhabited, each by peculiar species (or in some cases perhaps only
varieties) of some of the genera characterising the archipelago. So
that the small group of the Gala-

1 The Cape de Verde and
Galapagos Archipelagoes are compared in the Origin, Ed. i. p.
398, vi. p. 553. See also Journal of Researches, 1860, p. 393.

pagos Islands typifies, and follows exactly the same laws
in the distribution of its inhabitants, as a great continent. How
wonderful it is that two or three closely similar but distinct species
of a mocking-thrush1 should have been produced on three
neighbouring and absolutely similar islands; and that these three
species of mocking-thrush should be closely related to the other
species inhabiting wholly different climates and different districts of
America, and only in America. No similar case so striking as this of
the Galapagos Archipelago has hitherto been observed; and this
difference of the productions in the different islands may perhaps be
partly explained by the depth of the sea between them (showing that
they could not have been united within recent geological periods), and
by the currents of the sea sweeping straight between
them,—and by storms of wind being rare, through which means seeds and
birds
could be blown, or drifted, from one island to another. There are
however some similar facts: it is said that the different, though
neighbouring islands of the East Indian Archipelago are inhabited by
some different species of the same genera; and at the Sandwich group
some of the islands have each their peculiar species of the same genera
of plants.

Islands standing quite isolated within the intra-tropical
oceans have generally very peculiar floras, related, though feebly (as
in the case of St Helena2 where almost every species is
distinct), with the nearest continent: Tristan d'Acunha is feebly
related, I believe, in its plants, both to Africa and S. America, not
by having species in common, but

1 In the Origin, Ed.
i. p. 390, a strong point is made of birds which immigrated "with
facility and in a body" not having been modified. Thus the author
accounts for the small percentage of peculiar "marine birds."

2 "The affinities of the St
Helena flora are strongly South African." Hooker's Lecture on
Insular Floras in the Gardeners' Chronicle, Jan. 1867.

by the genera to which they belong1. The floras
of the numerous scattered islands of the Pacific are related to each
other and to all the surrounding continents; but it has been said, that
they have more of an Indo-Asiatic than American character2.
This is somewhat remarkable, as America is nearer to all the Eastern
islands, and lies in the direction of the trade-wind and prevailing
currents; on the other hand, all the heaviest gales come from the
Asiatic side. But even with the aid of these gales, it is not obvious
on the ordinary theory of creation how the possibility of migration
(without we suppose, with extreme improbability, that each species with
an Indo-Asiatic character has actually travelled from the Asiatic
shores, where such species do not now exist) explains this Asiatic
character in the plants of the Pacific. This is no more obvious than
that (as before remarked) there should exist a relation between the
creation of closely allied species in several regions of the world, and
the fact of many such species having wide ranges; and on the other
hand, of allied species confined to one region of the world having in
that region narrow ranges.

Alpine Floras.

We will now turn to the floras of mountain-summits which
are well known to differ from the floras of the neighbouring lowlands.
In certain characters, such as dwarfness of stature, hairiness,
&c., the species from the most distant mountains frequently
resemble each other,—a kind of analogy like that for instance of the
succulency of most desert plants. Besides this analogy, Alpine plants

1 It is impossible to make out
the precise form which the author intended to give to this sentence,
but the meaning is clear.

2 This is no doubt true, the
flora of the Sandwich group however has marked American affinities.

present some eminently curious facts in their
distribution. In some cases the summits of mountains, although
immensely distant from each other, are clothed by the same identical
species1 which are likewise the same with those growing on
the likewise very distant Arctic shores. In other cases, although few
or none of the species may be actually identical, they are closely
related; whilst the plants of the lowland districts surrounding the two
mountains in question will be wholly dissimilar. As mountain-summits,
as far as their plants are concerned, are islands rising out of an
ocean of land in which the Alpine species cannot live, nor across which
is there any known means of transport, this fact appears directly
opposed to the conclusion which we have come to from considering the
general distribution of organisms both on continents and on islands—namely,
that the degree of relationship between the inhabitants of two
points depends on the completeness and nature of the barriers between
those points2. I believe, however, this anomalous case
admits, as we shall presently see, of some explanation. We might have
expected that the flora of a mountain summit would have presented the
same relation to the flora of the surrounding lowland country, which
any isolated part of a continent does to the whole, or an island does
to the mainland, from which it is separated by a rather wide space of
sea. This in fact is the case with the plants clothing the summits of some mountains, which mountains it may be observed are particularly
isolated; for instance, all the species are peculiar, but they belong
to the forms characteristic of the surrounding continent, on the
mountains of Caraccas, of Van Dieman's

1 See Origin, Ed. i.
p. 365, vi. p. 515. The present discussion was written before the
publication of Forbes' celebrated paper on the same subject; see Life
and Letters, vol. I. p. 88.

2 The apparent breakdown of the
doctrine of barriers is slightly touched on in the Origin,
Ed. i. p. 365, vi. p. 515.

Land and of the Cape of Good Hope1. On some
other mountains, for instance <in> Tierra del Fuego and in Brazil, some
of the plants though distinct species are S. American forms; whilst
others are allied to or are identical with the Alpine species of
Europe. In islands of which the lowland flora is distinct <from> but
allied to that of the nearest continent, the Alpine plants are
sometimes (or perhaps mostly) eminently peculiar and distinct2;
this is the case on Teneriffe, and in a lesser degree even on some of
the Mediterranean islands.

If all Alpine floras had been characterised like that of
the mountain of Caraccas, or of Van Dieman's Land, &c., whatever
explanation is possible of the general laws of geographical
distribution would have applied to them. But the apparently anomalous
case just given, namely of the mountains of Europe, of some mountains
in the United States (Dr Boott) and of the summits of the Himalaya
(Royle), having many identical species in common conjointly with the
Arctic regions, and many species, though not identical, closely allied,
require a separate explanation. The fact likewise of several of the
species on the mountains of Tierra del Fuego (and in a lesser degree on
the mountains of Brazil) not belonging to American forms, but to those
of Europe, though so immensely remote, requires also a separate
explanation.

1 In the Origin, Ed.
i. p. 375, vi. p. 526, the author points out that on the mountains at
the Cape of Good Hope "some few representative European forms are
found, which have not been discovered in the inter-tropical parts of
Africa."

2 See Hooker's Lecture on
Insular Floras in the Gardeners' Chronicle, Jan. 1867.

Now we may with confidence affirm, from the number of the
then floating icebergs and low descent of the glaciers, that within a
period so near that species of shells have remained the same, the whole
of Central Europe and of North America (and perhaps of Eastern Asia)
possessed a very cold climate; and therefore it is probable that the
floras of these districts were the same as the present Arctic one,—as
is known to have been to some degree the case with then existing
sea-shells, and those now living on the Arctic shores. At this period
the mountains must have been covered with ice of which we have evidence
in the surfaces polished and scored by glaciers. What then would be the
natural and almost inevitable effects of the gradual change into the
present more temperate climate1? The ice and snow would
disappear from the mountains, and as new plants from the more temperate
regions of the south migrated northward, replacing the Arctic plants,
these latter would crawl2 up the now uncovered mountains,
and likewise be driven northward to the present Arctic shores. If the
Arctic flora of that period was a nearly uniform one, as the present
one is, then we should have the same plants on these mountain-summits
and on the present Arctic shores. On this view the Arctic flora of that
period must have been a widely extended one, more so than even the
present one; but considering how similar the physical conditions must
always be of land bordering on perpetual frost, this does not appear a
great difficulty; and may we not venture to suppose that

1 In the margin the author has
written "(Forbes)." This may have been inserted at a date later than
1844, or it may refer to a work by Forbes earlier than his Alpine paper.

the almost infinitely numerous icebergs, charged with
great masses of rocks, soil and brushwood1and
often driven high up on distant beaches, might have been the means of
widely distributing the seeds of the same species?

I will only hazard one other observation, namely that
during the change from an extremely cold climate to a more temperate
one the conditions, both on lowland and mountain, would be singularly
favourable for the diffusion of any existing plants, which could live
on land, just freed from the rigour of eternal winter; for it would
possess no inhabitants; and we cannot doubt that preoccupation2 is
the chief bar to the diffusion of plants. For amongst many other facts,
how otherwise can we explain the circumstance that the plants on the
opposite, though similarly constituted sides of a wide river in Eastern
Europe (as I was informed by Humboldt) should be widely different;
across which river birds, swimming quadrupeds and the wind must often
transport seeds; we can only suppose that plants already occupying the
soil and freely seeding check the germination of occasionally
transported seeds.

At about the same period when icebergs were transporting
boulders in N. America as far as 36° south, where the cotton tree now
grows in South America, in latitude 42° (where the land is now clothed
with forests having an almost tropical aspect with the trees bearing
epiphytes and intertwined with canes), the same ice action was going
on; is it not then in some degree probable that at this period the
whole tropical parts of the two Americas

possessed1 (as Falconer asserts that India did)
a more temperate climate? In this case the Alpine plants of the long
chain of the Cordillera would have descended much lower and there would
have been a broad high-road2 connecting those parts of North
and South America which were then frigid. As the present climate
supervened, the plants occupying the districts which now are become in
both hemispheres temperate and even semi-tropical must have been driven
to the Arctic and Antarctic3 regions; and only a few of the
loftiest points of the Cordillera can have retained their former
connecting flora. The transverse chain of Chiquitos might perhaps in a
similar manner during the ice-action period have served as a connecting
road (though a broken one) for Alpine plants to become dispersed from
the Cordillera to the highlands of Brazil. It may be observed that some
(though not strong) reasons can be assigned for believing that at about
this same period the two Americas were not so thoroughly divided as
they now are by the West Indies and tableland of Mexico. I will only
further remark that the present most singularly close similarity in the
vegetation of the lowlands of Kerguelen's Land4 and of
Tierra del Fuego (Hooker), though so far apart, may perhaps be
explained by the dissemination of seeds during this same cold period,
by means of icebergs, as before alluded to5.

Finally, I
think we may safely grant from the foregoing facts and reasoning that
the anomalous

1 Opposite to this passage, in
the margin, the author has written:—"too hypothetical."

2 The Cordillera is described as
supplying a great line of invasion in the Origin, Ed. i. p.
378.

3 This is an approximation to
the author's views on trans-tropical migration (Origin, Ed.
i. pp. 376-8). See Thiselton-Dyer's interesting discussion in Darwin
and Modern Science, p. 304.

4 See Hooker's Lecture on
Insular Floras in the Gardeners' Chronicle, Jan. 1867.

5 <Note by the author.>
Similarity of flora of coral islands easily explained.

similarity in the vegetation of certain very distant
mountain-summits is not in truth opposed to the conclusion of the
intimate relation subsisting between proximity in space (in accordance
with the means of transport in each class) and the degree of affinity
of the inhabitants of any two countries. In the case of several quite
isolated mountains, we have seen that the general law holds good.

Whether the same species
has been created more than
once.

As the fact of the same species of plants having been
found on mountain-summits immensely remote has been one chief cause of
the belief of some species having been contemporaneously produced or
created at two different points1, I will here briefly
discuss
this subject. On the ordinary theory of creation, we can see no reason
why on two similar mountain-summits two similar species may not have
been created; but the opposite view, independently of its simplicity,
has been generally received from the analogy of the general
distribution of all organisms, in which (as shown in this chapter) we
almost always find that great and continuous barriers separate distinct
series; and we are naturally led to suppose that the two series have
been separately created. When taking a more limited view we see a
river, with a quite similar country on both sides, with one side well
stocked with a certain animal and on the other side not one (as is the
case with the Bizcacha2 on the opposite sides of the Plata),
we are at once led to conclude that the Bizcacha

1 On centres of creation see Origin,
Ed. i. p. 352, vi. p. 499.

2 In the Journal of
Researches, Ed. 1860, p. 124, the distribution of the Bizcacha is
described as limited by the river Uruguay. The case is not I think
given in the Origin.

was produced on some one point or area on the western side
of the river. Considering our ignorance of the many strange chances of
diffusion by birds (which occasionally wander to immense distances) and
quadrupeds swallowing seeds and ova (as in the case of the flying
water-beetle which disgorged the eggs of a fish), and of whirlwinds
carrying seeds and animals into strong upper currents (as in the case
of volcanic ashes and showers of hay, grain and fish1), and
of the possibility of species having survived for short periods at
intermediate spots and afterwards becoming extinct there2;
and considering our knowledge of the great changes which have taken
place from subsidence and elevation in the surface of the earth, and of
our ignorance of the greater changes which may have taken
place, we ought to be very slow in admitting the probability of double
creations. In the case of plants on mountain-summits, I think I have
shown how almost necessarily they would, under the past conditions of
the northern hemisphere, be as similar as are the plants on the present
Arctic shores; and this ought to teach us a lesson of caution.

But the strongest argument against double creations may be
drawn from considering the case of mammifers3 in which, from
their nature and from the size of their offspring, the means of
distribution are more in view. There are no cases where the same
species is found in very remote localities,

1 In the Origin, Ed.
i. a special section (p. 356, vi. p. 504) is devoted to Means of
Dispersal. The much greater prominence given to this subject in
the Origin is partly accounted for by the author's
experiments being of later date, i.e. 1855 (Life and
Letters, vol. II. p. 53). The carriage of fish by
whirlwinds is
given in the Origin, Ed. i. p. 384, vi. p. 536.

2 The case of islands serving as
halting places is given in the Origin, Ed. i. p. 357, vi. p.
505. But here the evidence of this having occurred is supposed to be
lost by the subsidence of the islands, not merely by the extinction of
the species.

except where there is a continuous belt of land: the
Arctic region perhaps offers the strongest exception, and here we know
that animals are transported on icebergs1. The cases of
lesser difficulty may all receive a more or less simple explanation; I
will give only one instance; the nutria2, I believe, on the
eastern coast of S. America live exclusively in fresh-water rivers, and
I was much surprised how they could have got into rivulets, widely
apart, on the coast of Patagonia; but on the opposite coast I found
these quadrupeds living exclusively in the sea, and hence their
migration along the Patagonian coast is not surprising. There is no
case of the same mammifer being found on an island far from the coast,
and on the mainland, as happens with plants3. On the idea of
double creations it would be strange if the same species of several
plants should have been created in Australia and Europe; and no one
instance of the same species of mammifer having been created, or
aboriginally existing, in two as nearly remote and equally isolated
points. It is more philosophical, in such cases, as that of some plants
being found in Australia and Europe, to admit that we are ignorant of
the means of transport. I will allude only to one other case, namely,
that of the Mydas4, an Alpine animal, found only on the
distant peaks of the mountains of Java: who will pretend to deny that
during the ice period

2Nutria, is the
Spanish for otter, and is now a synonym for Lutra. The otter
on the Atlantic coast is distinguished by minute differences from the
Pacific species. Both forms are said to take to the sea. In fact the
case presents no especial difficulties.

3 In Origin, Ed. i. p.
394, vi. p. 548, bats are mentioned as an explicable exception to this
statement.

4 This reference is doubtless to Mydaus, a badger-like animal from the mountains of Java and
Sumatra (Wallace, Geographical Distribution, ii. p. 199). The
instance does not occur in the Origin but the author remarks
(Origin, Ed. i. p. 376, vi. p. 527) that cases, strictly
analogous to the distribution of plants, occur among terrestrial
mammals.

of the northern and southern hemispheres, and when India
is believed to have been colder, the climate might not have permitted
this animal to haunt a lower country, and thus to have passed along the
ridges from summit to summit? Mr Lyell has further observed that, as
in space, so in time, there is no reason to believe that after
the extinction of a species, the self-same form has ever reappeared1.
I think, then, we may, notwithstanding the many cases of difficulty,
conclude with some confidence that every species has been created or
produced on a single point or area.

On the number of species,
and of the classes to which
they belong in different regions.

The last fact in geographical distribution, which, as far
as I can see, in any way concerns the origin of species, relates to the
absolute number and nature of the organic beings inhabiting different
tracts of land. Although every species is admirably adapted (but not
necessarily better adapted than every other species, as we have seen in
the great increase of introduced species) to the country and station it
frequents; yet it has been shown that the entire difference between the
species in distant countries cannot possibly be explained by the
difference of the physical conditions of these countries. In the same
manner, I believe, neither the number of the species, nor the nature of
the great classes to which they belong, can possibly in all cases be
explained by the conditions of their country. New Zealand2,
a linear island stretching over about 700 miles of latitude, with
forests, marshes, plains and mountains reaching to the limits of
eternal snow, has far more

1 See Origin, Ed. i.
p. 313, vi. p. 454.

2 The comparison between New
Zealand and the Cape is given in the Origin, Ed. i. p. 389,
vi. p. 542.

diversified habitats than an equal area at the Cape of
Good Hope; and yet, I believe, at the Cape of Good Hope there are, of
phanerogamic plants, from five to ten times the number of species as in
all New Zealand. Why on the theory of absolute creations should this
large and diversified island only have from 400 to 500 (? Dieffenbach)
phanerogamic plants? and why should the Cape of Good Hope,
characterised by the uniformity of its scenery, swarm with more species
of plants than probably any other quarter of the world? Why on the
ordinary theory should the Galapagos Islands abound with terrestrial
reptiles? and why should many equal-sized islands in the Pacific be
without a single one1 or with only one or two species? Why
should the great island of New Zealand be without one mammiferous
quadruped except the mouse, and that was probably introduced with the
aborigines? Why should not one island (it can be shown, I think, that
the mammifers of Mauritius and St Iago have all been introduced) in the
open ocean possess a mammiferous quadruped? Let it not be said that
quadrupeds cannot live in islands, for we know that cattle, horses and
pigs during a long period have run wild in the West Indian and Falkland
Islands; pigs at St Helena; goats at Tahiti; asses in the Canary
Islands; dogs in Cuba; cats at Ascension; rabbits at Madeira and the
Falklands; monkeys at St Iago and the Mauritius; even elephants during
a long time in one of the very small Sooloo Islands; and European mice
on very many of the smallest islands far from the habitations of man2.
Nor let it be assumed that quadrupeds are more slowly created and hence
that the oceanic islands, which generally

1 In a corresponding discussion
in the Origin, Ed. i. p. 393, vi. p. 546, stress is laid on
the distribution of Batrachians not of reptiles.

are of volcanic formation, are of too recent origin to
possess them; for we know (Lyell) that new forms of quadrupeds succeed
each other quicker than Mollusca or Reptilia. Nor let it be assumed
(though such an assumption would be no explanation) that quadrupeds
cannot be created on small islands; for islands not lying in mid-ocean
do possess their peculiar quadrupeds; thus many of the smaller islands
of the East Indian Archipelago possess quadrupeds; as does Fernando Po
on the West Coast of Africa; as the Falkland Islands possess a peculiar
wolf-like fox1; so do the Galapagos Islands a peculiar mouse
of the S. American type. These two last are the most remarkable cases
with which I am acquainted; inasmuch as the islands lie further from
other land. It is possible that the Galapagos mouse may have been
introduced in some ship from the S. American coast (though the species
is at present unknown there), for the aboriginal species soon haunts
the goods of man, as I noticed in the roof of a newly erected shed in a
desert country south of the Plata. The Falkland Islands, though between
200 and 300 miles from the S. American coast, may in one sense be
considered as intimately connected with it; for it is certain that
formerly many icebergs loaded with boulders were stranded on its
southern coast, and the old canoes which are occasionally now stranded,
show that the currents still set from Tierra del Fuego. This fact,
however, does not explain the presence of the Canis antarcticus on
the Falkland Islands, unless we suppose that it formerly lived on the
mainland and became extinct there, whilst it survived on these islands,
to which it was borne (as happens with its northern congener, the
common wolf) on an iceberg, but this fact removes the anomaly of an
island, in appearance effectually separated

1 See Origin, Ed i. p.
393, vi. p. 547. The discussion is much fuller in the present Essay.

from other land, having its own species of quadruped, and
makes the case like that of Java and Sumatra, each having their own
rhinoceros.

Before summing up all the facts given in this section on
the present condition of organic beings, and endeavouring to see how
far they admit of explanation, it will be convenient to state all such
facts in the past geographical distribution of extinct beings as seem
anyway to concern the theory of descent.

SECTION SECOND.

Geographical distribution
of extinct organisms.

I have stated that if the land of the entire world be
divided into (we will say) three sections, according to the amount of
difference of the terrestrial mammifers inhabiting them, we shall have
three unequal divisions of (1st) Australia and its dependent islands,
(2nd) South America, (3rd) Europe, Asia and Africa. If we now look to
the mammifers which inhabited these three divisions during the later
Tertiary periods, we shall find them almost as distinct as at the
present day, and intimately related in each division to the existing
forms in that division1. This is wonderfully the case with
the several fossil Marsupial genera in the caverns of New South Wales
and even more wonderfully so in South America, where we have the same
peculiar group of monkeys, of a guanaco-like animal, of many rodents,
of the Marsupial Didelphys, of Armadilloes and other Edentata. This
last family is at present very characteristic of S. America, and in a
late Tertiary epoch it was even more so, as is shown by the numerous
enormous animals of the Megatheroid family, some

of which were protected by an osseous armour like that,
but on a gigantic scale, of the recent Armadillo. Lastly, over Europe
the remains of the several deer, oxen, bears, foxes, beavers,
field-mice, show a relation to the present inhabitants of this region;
and the contemporaneous remains of the elephant, rhinoceros,
hippopotamus, hyæna, show a relation with the grand Africo-Asiatic
division of the world. In Asia the fossil mammifers of the Himalaya
(though mingled with forms long extinct in Europe) are equally related
to the existing forms of the Africo-Asiatic division; but especially to
those of India itself. As the gigantic and now extinct quadrupeds of
Europe have naturally excited more attention than the other and smaller
remains, the relation between the past and the present mammiferous
inhabitants of Europe has not been sufficiently attended to. But in
fact the mammifers of Europe are at present nearly as much
Africo-Asiatic as they were formerly when Europe had its elephants and
rhinoceroses, etc.: Europe neither now nor then possessed peculiar
groups as does Australia and S. America. The extinction of certain
peculiar forms in one quarter does not make the remaining mammifers of
that quarter less related to its own great division of the world:
though Tierra del Fuego possesses only a fox, three rodents, and the
guanaco, no one (as these all belong to S. American types, but not to
the most characteristic forms) would doubt for one minute <as to>
classifying this district with S. America; and if fossil Edentata,
Marsupials and monkeys were to be found in Tierra del Fuego, it would
not make this district more truly S. American than it now is. So it is
with Europe1, and so far as

1 In the Origin, Ed.
i. p. 339, vi. p. 485, which corresponds to this part of the present
Essay, the author does not make a separate section for such cases as
the occurrence of fossil Marsupials in Europe (Origin, Ed. i.
p. 340, vi. p. 486) as he does in the present Essay; see the section on Changes in geographical distribution, p. 177.

is known with Asia, for the lately past and present
mammifers all belong to the Africo-Asiatic division of the world. In
every case, I may add, the forms which a country has is of more
importance in geographical arrangement than what it has not.

We find some evidence of the same general fact in a
relation between the recent and the Tertiary sea-shells, in the
different main divisions of the marine world.

This general and most remarkable relation between the
lately past and present mammiferous inhabitants of the three main
divisions of the world is precisely the same kind of fact as the
relation between the different species of the several sub-regions of
any one of the main divisions. As we usually associate great physical
changes with the total extinction of one series of beings, and its
succession by another series, this identity of relation between the
past and the present races of beings in the same quarters of the globe
is more striking than the same relation between existing beings in
different sub-regions: but in truth we have no reason for supposing
that a change in the conditions has in any of these cases supervened,
greater than that now existing between the temperate and tropical, or
between the highlands and lowlands of the same main divisions, now
tenanted by related beings. Finally, then, we clearly see that in each
main division of the world the same relation holds good between its
inhabitants in time as over space1.

1 "We can understand how it is
that all the forms of life, ancient and recent, make together one grand
system; for all are connected by generation." Origin, Ed. i.
p. 344, vi. p. 491.

If, however, we look closer, we shall find that even
Australia, in possessing a terrestrial Pachyderm, was so far less
distinct from the rest of the world than it now is; so was S. America
in possessing the Mastodon, horse, [hyæna,]1 and antelope.
N. America, as I have remarked, is now, in its mammifers, in some
respects neutral ground between S. America and the great Africo-Asiatic
division; formerly, in possessing the horse, Mastodon and three
Megatheroid animals, it was more nearly related to S. America; but in
the horse and Mastodon, and likewise in having the elephant, oxen,
sheep, and pigs, it was as much, if not more, related to the
Africo-Asiatic division. Again, northern India was much more closely
related (in having the giraffe, hippopotamus, and certain musk-deer) to
southern Africa than it now is; for southern and eastern Africa
deserve, if we divide the world into five parts, to make one division
by itself. Turning to the dawn of the Tertiary period, we must, from
our ignorance of other portions of the world, confine ourselves to
Europe; and at that period, in the presence of Marsupials2 and Edentata, we behold an entire blending of those
mammiferous forms which now eminently characterise Australia and S.
America3.

If we now look at the distribution of sea-shells, we find
the same changes in distribution. The Red Sea and the Mediterranean
were more nearly related in these shells than they now are. In
different parts of Europe, on the other hand, during the

1 The word hyæna is
erased. There appear to be no fossil Hyænidæ in S. America.

2 See note 1, p. 175, also Origin,
Ed. i. p. 340, vi. p. 486.

3 <Note by the author.> And see
Eocene European mammals in N. America.

Miocene period, the sea-shells seem to have been more
different than at present. In1 the Tertiary period,
according to Lyell, the shells of N. America and Europe were less
related than at present, and during the Cretaceous still less like;
whereas, during this same Cretaceous period, the shells of India and
Europe were more like than at present. But going further back to the
Carbonaceous period, in N. America and Europe, the productions were
much more like than they now are2. These facts harmonise
with the conclusions drawn from the present distribution of organic
beings, for we have seen, that from species being created in different
points or areas, the formation of a barrier would cause or make two
distinct geographical areas; and the destruction of a barrier would
permit their diffusion3. And as long-continued geological
changes must both destroy and make barriers, we might expect, the
further we looked backwards, the more changed should we find the
present distribution. This conclusion is worthy of attention; because,
finding in widely different parts of the same main division of the
world, and in volcanic islands near them, groups of distinct, but
related, species;—and finding that a singularly analogous relation
holds good with respect to the beings of past times, when none of the
present species were living, a person might be tempted to believe in
some mystical relation between certain areas of the world, and the
production of certain organic forms; but we now see that such an
assumption would have to be complicated by the admission that such a
relation, though holding good for long revolutions of years, is not
truly persistent.

section. Geologists finding in the most remote period with
which we are acquainted, namely in the Silurian period, that the shells
and other marine productions1 in North and South America, in
Europe, Southern Africa, and Western Asia, are much more similar than
they now are at these distant points, appear to have imagined that in
these ancient times the laws of geographical distribution were quite
different than what they now are: but we have only to suppose that
great continents were extended east and west, and thus did not divide
the inhabitants of the temperate and tropical seas, as the continents
now do; and it would then become probable that the inhabitants of the
seas would be much more similar than they now are. In the immense space
of ocean extending from the east coast of Africa to the eastern islands
of the Pacific, which space is connected either by lines of tropical
coast or by islands not very distant from each other, we know (Cuming)
that many shells, perhaps even as many as 200, are common to the
Zanzibar coast, the Philippines, and the eastern islands of the Low or
Dangerous Archipelago in the Pacific. This space equals that from the
Arctic to the Antarctic pole! Pass over the space of quite open ocean,
from the Dangerous Archipelago to the west coast of S. America, and
every shell is different: pass over the narrow space of S. America, to
its eastern shores, and again every shell is different! Many fish, I
may add, are also common to the Pacific and Indian Oceans.

Let us sum up the several facts now given with respect to
the past and present geographical distribution of organic beings. In a
previous chapter it was shown that species are not exterminated by
universal catastrophes, and that they are slowly produced: we have also
seen that each species is probably only once produced, on one point or
area once in time; and that each diffuses itself, as far as barriers
and its conditions of life permit. If we look at any one main division
of the land, we find in the different parts, whether exposed to
different conditions or to the same conditions, many groups of species
wholly or nearly distinct as species, nevertheless intimately related.
We find the inhabitants of islands, though distinct as species,
similarly related to the inhabitants of the nearest continent; we find
in some cases, that even the different islands of one such group are
inhabited by species distinct, though intimately related to one another
and to those of the nearest continent:—thus typifying the distribution
of organic beings over the whole world. We find the floras of distant
mountain-summits either very similar (which seems to admit, as shown,
of a simple explanation) or very distinct but related to the floras of
the surrounding region; and hence, in this latter case, the floras of
two mountain-summits, although exposed to closely similar conditions,
will be very different. On the mountain-summits of islands,
characterised by peculiar faunas and floras, the plants are often
eminently peculiar. The dissimilarity of the organic beings inhabiting
nearly similar countries is best seen by comparing the main divisions
of the world; in each of which some districts may be found very
similarly

exposed, yet the inhabitants are wholly unlike;—far more
unlike than those in very dissimilar districts in the same main
division. We see this strikingly in comparing two volcanic
archipelagoes, with nearly the same climate, but situated not very far
from two different continents; in which case their inhabitants are
totally unlike. In the different main divisions of the world, the
amount of difference between the organisms, even in the same class, is
widely different, each main division having only the species distinct
in some families, in other families having the genera distinct. The
distribution of aquatic organisms is very different from that of the
terrestrial organisms; and necessarily so, from the barriers to their
progress being quite unlike. The nature of the conditions in an
isolated district will not explain the number of species inhabiting it;
nor the absence of one class or the presence of another class. We find
that terrestrial mammifers are not present on islands far removed from
other land. We see in two regions, that the species though distinct are
more or less related, according to the greater or less possibility of the transportal in past and present times of species from one
to the other region; although we can hardly admit that all the species
in such cases have been transported from the first to the second
region, and since have become extinct in the first: we see this law in
the presence of the fox on the Falkland Islands; in the European
character of some of the plants of Tierra del Fuego; in the
Indo-Asiatic character of the plants of the Pacific; and in the
circumstance of those genera which range widest having many species
with wide ranges; and those genera with restricted ranges having
species with restricted ranges. Finally, we find in each of the main
divisions of the land, and probably of the sea, that the existing
organisms are related to those lately extinct.

Looking further backwards we see that the past
geographical distribution of organic beings was different from the
present; and indeed, considering that geology shows that all our land
was once under water, and that where water now extends land is forming,
the reverse could hardly have been possible.

Now these several facts, though evidently all more or less
connected together, must by the creationist (though the geologist may
explain some of the anomalies) be considered as so many ultimate facts.
He can only say, that it so pleased the Creator that the organic beings
of the plains, deserts, mountains, tropical and temperature forests, of
S. America, should all have some affinity together; that the
inhabitants of the Galapagos Archipelago should be related to those of
Chile; and that some of the species on the similarly constituted
islands of this archipelago, though most closely related, should be
distinct; that all its inhabitants should be totally unlike those of
the similarly volcanic and arid Cape de Verde and Canary Islands; that
the plants on the summit of Teneriffe should be eminently peculiar;
that the diversified island of New Zealand should have not many plants,
and not one, or only one, mammifer; that the mammifers of S. America,
Australia and Europe should be clearly related to their ancient and
exterminated prototypes; and so on with other facts. But it is
absolutely opposed to every analogy, drawn from the laws imposed by the
Creator on inorganic matter, that facts, when connected, should be
considered as ultimate and not the direct consequences of more general
laws.

An attempt to explain the foregoing
laws of geographical distribution, on the theory of allied species
having a common descent.

First let us recall the circumstances most favourable for
variation under domestication, as given in the first chapter—viz.
1st,
a change, or repeated changes, in the conditions to which the organism
has been exposed, continued through several seminal (i.e. not
by buds or divisions) generations: 2nd, steady selection of the slight
varieties thus generated with a fixed end in view: 3rd, isolation as
perfect as possible of such selected varieties; that is, the preventing
their crossing with other forms; this latter condition applies to all
terrestrial animals, to most if not all plants and perhaps even to most
(or all) aquatic organisms. It will be convenient here to show the
advantage of isolation in the formation of a new breed, by comparing
the progress of two persons (to neither of whom let time be of any
consequence) endeavouring to select and form some very peculiar new
breed. Let one of these persons work on the vast herds of cattle in the
plains of La Plata1, and the other on a small stock of 20 or
30 animals in an island. The latter might have to wait centuries (by
the hypothesis of no importance)2 before he obtained a
"sport" approaching to what he wanted; but when he did and saved the
greater number of its offspring and their offspring again, he might
hope that his whole little stock would be in some degree affected, so
that by continued selection he might

1 This instance occurs in the
Essay of 1842, p. 32, but not in the Origin; though the
importance of isolation is discussed (Origin, Ed. i. p. 104,
vi. p. 127).

gain his end. But on the Pampas, though the man might get
his first approach to his desired form sooner, how hopeless would it be
to attempt, by saving its offspring amongst so many of the common kind,
to affect the whole herd: the effect of this one peculiar "sport1"
would be quite lost before he could obtain a second original sport of
the same kind. If, however, he could separate a small number of cattle,
including the offspring of the desirable "sport," he might hope, like
the man on the island, to effect his end. If there be organic beings of
which two individuals never unite, then simple selection
whether on a continent or island would be equally serviceable to make a
new and desirable breed; and this new breed might be made in
surprisingly few years from the great and geometrical powers of
propagation to beat out the old breed; as has happened (notwithstanding
crossing) where good breeds of dogs and pigs have been introduced into
a limited country,—for instance, into the islands of the Pacific.

Let us now take the simplest natural case of an islet
upheaved by the volcanic or subterranean forces in a deep sea, at such
a distance from other land that only a few organic beings at rare
intervals were transported to it, whether borne by the sea2 (like
the seeds of plants to coral-reefs), or by hurricanes, or by floods, or
on rafts, or in roots of large trees, or the germs of one plant or
animal attached to or in the stomach of some other animal, or by the
intervention (in most cases the most probable means) of other islands
since sunk or destroyed. It may be remarked that when one part of the
earth's crust is raised it is probably the

1 It is unusual to find the
author speaking of the selection of sports rather than small
variations.

2 This brief discussion is
represented in the Origin, Ed. i. by a much fuller one (pp.
356, 383, vi. pp. 504, 535). See, however, the section in the present
Essay, p. 168.

general rule that another part sinks. Let this island go
on slowly, century after century, rising foot by foot; and in the
course of time we shall have instead <of> a small mass of rock1,
lowland and highland, moist woods and dry sandy spots, various soils,
marshes, streams and pools: under water on the sea shore, instead of a
rocky steeply shelving coast we shall have in some parts bays with mud,
sandy beaches and rocky shoals. The formation of the island by itself
must often slightly affect the surrounding climate. It is impossible
that the first few transported organisms could be perfectly adapted to
all these stations; and it will be a chance if those successively
transported will be so adapted. The greater number would probably come
from the lowlands of the nearest country; and not even all these would
be perfectly adapted to the new islet whilst it continued low and
exposed to coast influences. Moreover, as it is certain that all
organisms are nearly as much adapted in their structure to the other
inhabitants of their country as they are to its physical conditions, so
the mere fact that a few beings (and these taken in great
degree by chance) were in the first case transported to the islet,
would in itself greatly modify their conditions2. As the
island continued rising we might also expect an occasional new
visitant; and I repeat that even one new being must often affect beyond
our calculation by occupying the room and taking part of the
subsistence of another (and this again from another and so on), several
or many other organisms. Now as the first transported and any
occasional successive visitants spread or tended to spread over the
growing island, they would undoubtedly be exposed through several
generations to new and varying conditions: it might also easily happen
that some of

1 On the formation of new
stations, see Origin, Ed. i. p. 292, vi. p. 429.

the species on an average might obtain an
increase of food, or food of a more nourishing quality1.
According then to every analogy with what we have seen takes place in
every country, with nearly every organic being under domestication, we
might expect that some of the inhabitants of the island would "sport,"
or have their organization rendered in some degree plastic. As the
number of the inhabitants are supposed to be few and as all these
cannot be so well adapted to their new and varying conditions as they
were in their native country and habitat, we cannot believe that every
place or office in the economy of the island would be as well filled as
on a continent where the number of aboriginal species is far greater
and where they consequently hold a more strictly limited place. We
might therefore expect on our island that although very many slight
variations were of no use to the plastic individuals, yet that
occasionally in the course of a century an individual might be born2 of which the structure or constitution in some slight degree would
allow it better to fill up some office in the insular economy and to
struggle against other species. If such were the case the individual
and its offspring would have a better chance of surviving
and of beating out its parent form; and if (as is probable) it and its
offspring crossed with the unvaried parent form, yet the number of the
individuals being not very great, there would be a chance of the new
and more serviceable form being nevertheless in some slight degree
preserved. The struggle for existence would go on annually selecting
such individuals until a new race or species was formed. Either few or
all the first visitants to the island might become modified, ac-

1 In the MS. some
of the
species...nourishing quality is doubtfully erased. It seems clear
that he doubted whether such a problematical supply of food would be
likely to cause variation.

2 At this time the author
clearly put more faith in the importance of sport-like variation than
in later years.

cording as the physical conditions of the island and those
resulting from the kind and number of other transported species were
different from those of the parent country—according
to the
difficulties offered to fresh immigration—and
according to the length
of time since the first inhabitants were introduced. It is obvious that
whatever was the country, generally the nearest from which the first
tenants were transported, they would show an affinity, even if all had
become modified, to the natives of that country and even if the
inhabitants of the same source (?) had been modified. On this view we
can at once understand the cause and meaning of the affinity of the
fauna and flora of the Galapagos Islands with that of the coast of S.
America; and consequently why the inhabitants of these islands show not
the smallest affinity with those inhabiting other volcanic islands,
with a very similar climate and soil, near the coast of Africa1.

To return once again to our island, if by the continued
action of the subterranean forces other neighbouring islands were
formed, these would generally be stocked by the inhabitants of the
first island, or by a few immigrants from the neighbouring mainland;
but if considerable obstacles were interposed to any communication
between the terrestrial productions of these islands, and their
conditions were different (perhaps only by the number of different
species on each island), a form transported from one island to another
might become altered in the same manner as one from the continent; and
we should have several of the islands tenanted by representative races
or species, as is so wonderfully the case with the different islands of
the Galapagos Archipelago. As the islands become mountainous, if
mountain-species were not introduced, as could rarely happen, a greater
amount of variation and

selection would be requisite to adapt the species, which
originally came from the lowlands of the nearest continent, to the
mountain-summits than to the lower districts of our islands. For the
lowland species from the continent would have first to struggle against
other species and other conditions on the coast-land of the island, and
so probably become modified by the selection of its best fitted
varieties, then to undergo the same process when the land had attained
a moderate elevation; and then lastly when it had become Alpine. Hence
we can understand why the faunas of insular mountain-summits are, as in
the case of Teneriffe, eminently peculiar. Putting on one side the case
of a widely extended flora being driven up the mountain-summits, during
a change of climate from cold to temperate, we can see why in other
cases the floras of mountain-summits (or as I have called them islands
in a sea of land) should be tenanted by peculiar species, but related
to those of the surrounding lowlands, as are the inhabitants of a real
island in the sea to those of the nearest continent1.

Let us now consider the effect of a change of climate or
of other conditions on the inhabitants of a continent and of an
isolated island without any great change of level. On a continent the
chief effects would be changes in the numerical proportion of the
individuals of the different species; for whether the climate became
warmer or colder, drier or damper, more uniform or extreme, some
species are at present adapted to its diversified districts; if for
instance it became cooler, species would migrate from its more
temperate parts and from its higher land; if damper, from its damper

1 See Origin, Ed. i.
p. 403, vi. p. 558, where the author speaks of Alpine humming birds,
rodents, plants, &c. in S. America, all of strictly American forms.
In the MS. the author has added between the lines "As
world has been
getting hotter, there has been radiation from high-lands,—old
view?—curious; I presume
Diluvian in origin."

regions, &c. On a small and isolated island, however,
with few species, and these not adapted to much diversified conditions,
such changes instead of merely increasing the number of certain species
already adapted to such conditions, and decreasing the number of other
species, would be apt to affect the constitutions of some of the
insular species: thus if the island became damper it might well happen
that there were no species living in any part of it adapted to the
consequences resulting from more moisture. In this case therefore, and
still more (as we have seen) during the production of new stations from
the elevation of the land, an island would be a far more fertile
source, as far as we can judge, of new specific forms than a continent.
The new forms thus generated on an island, we might expect, would
occasionally be transported by accident, or through long-continued
geographical changes be enabled to emigrate and thus become slowly
diffused.

But if we look to the origin of a continent; almost every
geologist will admit that in most cases it will have first existed as
separate islands which gradually increased in size1; and
therefore all that which has been said concerning the probable changes
of the forms tenanting a small archipelago is applicable to a continent
in its early state. Furthermore, a geologist who reflects on the
geological history of Europe (the only region well known) will admit
that it has been many times depressed, raised and left stationary.
During the sinking of a continent and the probable generally
accompanying changes of climate the effect would be little, except on the numerical proportions and in the extinction (from the
lessening of rivers, the drying of marshes

1 See the comparison between the
Malay Archipelago and the probable former state of Europe, Origin,
Ed. i. p. 299, vi. p. 438, also Origin, Ed. i. p. 292, vi. p.
429.

and the conversion of high-lands into low &c.) of some
or of many of the species. As soon however as the continent became
divided into many isolated portions or islands, preventing free
immigration from one part to another, the effect of climatic and other
changes on the species would be greater. But let the now broken
continent, forming isolated islands, begin to rise and new stations
thus to be formed, exactly as in the first case of the upheaved
volcanic islet, and we shall have equally favourable conditions for the
modification of old forms, that is the formation of new races or
species. Let the islands become reunited into a continent; and then the
new and old forms would all spread, as far as barriers, the means of
transportal, and the pre-occupation of the land by other species, would
permit. Some of the new species or races would probably become extinct,
and some perhaps would cross and blend together. We should thus have a
multitude of forms, adapted to all kinds of slightly different
stations, and to diverse groups of either antagonist or food-serving
species. The oftener these oscillations of level had taken place (and
therefore generally the older the land) the greater the number of
species <which> would tend to be formed. The inhabitants of a continent
being thus derived in the first stage from the same original parents,
and subsequently from the inhabitants of one wide area, since often
broken up and reunited, all would be obviously related together and the
inhabitants of the most dissimilar stations on the same
continent would be more closely allied than the inhabitants of two very similar stations on two of the main divisions of the world1.

I need hardly point out that we now can ob-

1Origin, Ed. i. p.
349, vi. p. 496. The arrangement of the argument in the present Essay
leads to repetition of statements made in the earlier part of the book:
in the Origin this is avoided.

viously see why the number of species in two districts,
independently of the number of stations in such districts, should be in
some cases as widely different as in New Zealand and the Cape of Good
Hope1. We can see, knowing the difficulty in the transport
of terrestrial mammals, why islands far from mainlands do not possess
them2; we see the general reason, namely accidental
transport (though not the precise reason), why certain islands should,
and others should not, possess members of the class of reptiles. We can
see why an ancient channel of communication between two distant points,
as the Cordillera probably was between southern Chile and the United
States during the former cold periods; and icebergs between the
Falkland Islands and Tierra del Fuego; and gales, at a former or
present time, between the Asiatic shores of the Pacific and eastern
islands in this ocean; is connected with (or we may now say causes) an
affinity between the species, though distinct, in two such districts.
We can see how the better chance of diffusion, from several of the
species of any genus having wide ranges in their own countries,
explains the presence of other species of the same genus in other
countries3; and on the other hand, of species of restricted
powers of ranging, forming genera with restricted ranges.

As every one would be surprised if two exactly similar but
peculiar varieties4 of any species were raised by man by
long continued selection, in two different countries, or at two very
different periods, so we ought not to expect that an exactly similar
form would be produced from the modification of an old one in two
distinct countries or at two distinct

periods. For in such places and times they would probably
be exposed to somewhat different climates and almost certainly to
different associates. Hence we can see why each species appears to have
been produced singly, in space and in time. I need hardly remark that,
according to this theory of descent, there is no necessity of
modification in a species, when it reaches a new and isolated country.
If it be able to survive and if slight variations better adapted to the
new conditions are not selected, it might retain (as far as we can see)
its old form for an indefinite time. As we see that some sub-varieties
produced under domestication are more variable than others, so in
nature, perhaps, some species and genera are more variable than others.
The same precise form, however, would probably be seldom preserved
through successive geological periods, or in widely and differently
conditioned countries1.

Finally, during the long periods of time and probably of
oscillations of level, necessary for the formation of a continent, we
may conclude (as above explained) that many forms would become extinct.
These extinct forms, and those surviving (whether or not modified and
changed in structure), will all be related in each continent in the
same manner and degree, as are the inhabitants of any two different
sub-regions in that same continent. I do not mean to say that, for
instance, the present Marsupials of Australia or Edentata and rodents
of S. America have descended from any one of the few fossils of the
same orders which have been discovered in these countries. It is
possible that, in a very few instances, this may be the case; but
generally they must be considered as merely codescendants of common
stocks2. I believe in this, from the improbability,
considering the vast number of species, which (as

explained in the last chapter) must by our theory have
existed, that the comparatively few fossils which have been
found should chance to be the immediate and linear progenitors of those
now existing. Recent as the yet discovered fossil mammifers of S.
America are, who will pretend to say that very many intermediate forms
may not have existed? Moreover, we shall see in the ensuing chapter
that the very existence of genera and species can be explained only by
a few species of each epoch leaving modified successors or new species
to a future period; and the more distant that future period, the fewer
will be the linear heirs of the former epoch. As by our
theory, all mammifers must have descended from the same parent stock,
so is it necessary that each land now possessing terrestrial mammifers
shall at some time have been so far united to other land as to permit
the passage of mammifers1; and it accords with this
necessity, that in looking far back into the earth's history we find,
first changes in the geographical distribution, and secondly a period
when the mammiferous forms most distinctive of two of the present main
divisions of the world were living together2.

I think then I am justified in asserting that most of the
above enumerated and often trivial points in the geographical
distribution of past and present organisms (which points must be viewed
by the creationists as so many ultimate facts) follow as a simple
consequence of specific forms being mutable and of their being adapted
by natural selection to diverse ends, conjoined with their powers of
dispersal, and the geologico-geographical changes now in slow progress
and which undoubtedly have taken place. This large class of facts being
thus explained,

There is one observation of considerable importance that
may be here introduced, with regard to the improbability of the chief
transitional forms between any two species being found fossil. With
respect to the finer shades of transition, I have before remarked that
no one has any cause to expect to trace them in a fossil state, without
he be bold enough to imagine that geologists at a future epoch will be
able to trace from fossil bones the gradations between the Short-Horns,
Herefordshire, and Alderney breeds of cattle1. I have
attempted to show that rising islands, in process of formation, must be
the best nurseries of new specific forms, and these points are the
least favourable for the embedment of fossils2: I appeal, as
evidence, to the state of the numerous scattered islands in
the several great oceans: how rarely do any sedimentary deposits occur
on them; and when present they are mere narrow fringes of no great
antiquity, which the sea is generally wearing away and destroying. The
cause of this lies in isolated islands being generally volcanic and
rising points; and the effects of subterranean elevation is to bring up
the surrounding newly-deposited strata within the destroying action of
the coast-waves: the strata, deposited at greater distances, and
therefore in the depths of the ocean, will be almost barren of organic
remains. These

1Origin, Ed. i. p.
299, vi. p. 437.

2 "Nature may almost be said to
have guarded against the frequent discovery of her transitional or
linking forms," Origin, Ed. i. p. 292. A similar but not
identical passage occurs in Origin, Ed. vi. p. 428.

remarks may be generalised:—periods of subsidence will
always be most favourable to an accumulation of great thicknesses of
strata, and consequently to their long preservation; for without one
formation be protected by successive strata, it will seldom be
preserved to a distant age, owing to the enormous amount of denudation,
which seems to be a general contingent of time1. I may
refer, as evidence of this remark, to the vast amount of subsidence
evident in the great pile of the European formations, from the Silurian
epoch to the end of the Secondary, and perhaps to even a later period.
Periods of elevation on the other hand cannot be favourable to the
accumulation of strata and their preservation to distant ages, from the
circumstance just alluded to, viz. of elevation tending to bring to the
surface the circum-littoral strata (always abounding most in fossils)
and destroying them. The bottom of tracts of deep water (little
favourable, however, to life) must be excepted from this unfavourable
influence of elevation. In the quite open ocean, probably no sediment2 is accumulating, or at a rate so slow as not to preserve fossil
remains, which will always be subject to disintegration. Caverns, no
doubt, will be equally likely to preserve terrestrial fossils in
periods of elevation and of subsidence; but whether it be owing to the
enormous amount of denudation, which all land seems to have undergone,
no cavern with fossil bones has been found belonging to the Secondary
period3.

Hence many more remains will be preserved to a distant
age, in any region of the world, during periods of its subsidence4,
than of its elevation.

But during the subsidence of a tract of land, its
inhabitants (as before shown) will from the decrease of space and of
the diversity of its stations, and from the land being fully
preoccupied by species fitted to diversified means of subsistence, be
little liable to modification from selection, although many may, or
rather must, become extinct. With respect to its circum-marine
inhabitants, although during a change from a continent to a great archipelago,
the number of stations fitted for marine beings will be increased,
their means of diffusion (an important check to change of form) will be
greatly improved; for a continent stretching north and south, or a
quite open space of ocean, seems to be to them the only barrier. On the
other hand, during the elevation of a small archipelago and its
conversion into a continent, we have, whilst the number of stations are
increasing, both for aquatic and terrestrial productions, and whilst
these stations are not fully preoccupied by perfectly adapted species,
the most favourable conditions for the selection of new specific forms;
but few of them in their early transitional states will be preserved to
a distant epoch. We must wait during an enormous lapse of time, until
long-continued subsidence shall have taken the place in this quarter of
the world of the elevatory process, for the best conditions of the
embedment and the preservation of its inhabitants. Generally the great
mass of the strata in every country, from having been chiefly
accumulated during subsidence, will be the tomb, not of transitional
forms, but of those either becoming extinct or remaining unmodified.

The state of our knowledge, and the slowness of the
changes of level, do not permit us to test the truth of these remarks,
by observing whether there are more transitional or "fine" (as
naturalists would term them) species, on a rising and enlarging

tract of land, than on an area of subsidence. Nor do I
know whether there are more "fine" species on isolated volcanic islands
in process of formation, than on a continent; but I may remark, that at
the Galapagos Archipelago the number of forms, which according to some
naturalists are true species, and according to others are mere races,
is considerable: this particularly applies to the different species or
races of the same genera inhabiting the different islands of this
archipelago. Furthermore it may be added (as bearing on the great facts
discussed in this chapter) that when naturalists confine their
attention to any one country, they have comparatively little difficulty
in determining what forms to call species and what to call varieties;
that is, those which can or cannot be traced or shown to be probably
descendants of some other form: but the difficulty increases, as
species are brought from many stations, countries and islands. It was
this increasing (but I believe in few cases insuperable) difficulty
which seems chiefly to have urged Lamarck to the conclusion that
species are mutable.

IT has been observed from the earliest times that organic
beings fall into groups2, and these groups into others of
several values, such as species into genera, and then into
sub-families, into families, orders, &c. The same fact holds with
those beings which no longer exist. Groups of species seem to follow
the same laws in their appearance and extinction3, as do the
individuals of any one species: we have reason to believe that, first,
a few species appear, that their numbers increase; and that, when
tending to extinction, the numbers of the species decrease, till
finally the group becomes extinct, in the same way as a species becomes
extinct, by the individuals becoming rarer and rarer. Moreover, groups,
like the individuals of a species, appear to become extinct at
different times in different countries. The Palæotherium was extinct

1 Ch. XIII of the Origin,
Ed. i., Ch. XIV Ed. vi. begins with a similar statement. In the present
Essay the author adds a note:—"The obviousness of the fact <i.e. the
natural grouping of organisms> alone prevents it being remarkable. It
is scarcely explicable by creationist: groups of aquatic, of vegetable
feeders and carnivorous, &c., might resemble each other; but why as
it is. So with plants,—analogical resemblance thus accounted for. Must
not here enter into details." This argument is incorporated with the
text in the Origin, Ed. i.

much sooner in Europe than in India: the Trigonia1 was
extinct in early ages in Europe, but now lives in the seas of
Australia. As it happens that one species of a family will endure for a
much longer period than another species, so we find that some whole
groups, such as Mollusca, tend to retain their forms, or to remain
persistent, for longer periods than other groups, for instance than the
Mammalia. Groups therefore, in their appearance, extinction, and rate
of change or succession, seem to follow nearly the same laws with the
individuals of a species2.

What is the Natural System?

The proper arrangement of species into groups, according
to the natural system, is the object of all naturalists; but scarcely
two naturalists will give the same answer to the question, What is the
natural system and how are we to recognise it? The most important
characters3 it might be thought (as it was by the earliest
classifiers) ought to be drawn from those parts of the structure which
determine its habits and place in the economy of nature, which we may
call the final end of its existence. But nothing is further from the
truth than this; how much external resemblance there is between the
little otter (Chironectes) of Guiana and the common otter; or again
between the common swallow and the swift; and who can doubt that the
means and ends of their existence are closely similar, yet how grossly
wrong would be the classification, which put close to each other a
Marsupial and Placental animal, and two birds with widely different
skeletons. Relations, such as in the two latter cases, or as that

1Origin, Ed. i. p.
321, vi. p. 463.

2 In the Origin, Ed.
i. this preliminary matter is replaced (pp. 411, 412, vi. pp. 566, 567)
by a discussion in which extinction is also treated, but chiefly from
the point of view of the theory of divergence.

between the whale and fishes, are denominated "analogical1,"
or are sometimes described as "relations of adaption." They are
infinitely numerous and often very singular; but are of no use in the
classification of the higher groups. How it comes, that certain parts
of the structure, by which the habits and functions of the species are
settled, are of no use in classification, whilst other parts, formed at
the same time, are of the greatest, it would be difficult to say, on
the theory of separate creations.

Some authors as Lamarck, Whewell &c., believe that the
degree of affinity on the natural system depends on the degrees of
resemblance in organs more or less physiologically important for the
preservation of life. This scale of importance in the organs is
admitted to be of difficult discovery. But quite independent of this,
the proposition, as a general rule, must be rejected as false; though
it may be partially true. For it is universally admitted that the same
part or organ, which is of the highest service in classification in one
group, is of very little use in another group, though in both groups,
as far as we can see, the part or organ is of equal physiological
importance: moreover, characters quite unimportant physiologically,
such as whether the covering of the body consists of hair or feathers,
whether the nostrils communicated with the mouth2 &c.,
&c., are of the highest generality in classification; even colour,
which is so inconstant in many species, will sometimes well
characterise even a whole group of species. Lastly, the fact, that no
one character is of so much importance in determining to what great
group an organism belongs, as the forms through which the embryo3 passes from the germ upwards to maturity, cannot be reconciled

with the idea that natural classification follows
according to the degrees of resemblance in the parts of most
physiological importance. The affinity of the common rock-barnacle with
the Crustaceans can hardly be perceived in more than a single character
in its mature state, but whilst young, locomotive, and furnished with
eyes, its affinity cannot be mistaken1. The cause of the
greater value of characters, drawn from the early stages of life, can,
as we shall in a succeeding chapter see, be in a considerable degree
explained, on the theory of descent, although inexplicable on the views
of the creationist.

Practically, naturalists seem to classify according to the
resemblance of those parts or organs which in related groups are most
uniform, or vary least2: thus the æstivation, or manner in
which the petals etc. are folded over each other, is found to afford an
unvarying character in most families of plants, and accordingly any
difference in this respect would be sufficient to cause the rejection
of a species from many families; but in the Rubiaceæ the æstivation is
a varying character, and a botanist would not lay much stress on it, in
deciding whether or not to class a new species in this family. But this
rule is obviously so arbitrary a formula, that most naturalists seem to
be convinced that something ulterior is represented by the natural
system; they appear to think that we only discover by such similarities
what the arrangement of the system is, not that such similarities make
the system. We can only thus understand Linnæus'3 well-known saying, that the characters do not make the genus; but that
the genus gives the characters: for a classification, independent of
characters, is here presupposed.

Hence many naturalists have said that the natural system
reveals the plan of the Creator: but without it be specified whether
order in time or place, or what else is meant by the plan of the
Creator, such expressions appear to me to leave the question exactly
where it was.

Some naturalists consider that the geographical position1 of a species may enter into the consideration of the group into which
it should be placed; and most naturalists (either tacitly or openly)
give value to the different groups, not solely by their relative
differences in structure, but by the number of forms included in them.
Thus a genus containing a few species might be, and has often been,
raised into a family on the discovery of several other species. Many
natural families are retained, although most closely related to other
families, from including a great number of closely similar species. The
more logical naturalist would perhaps, if he could, reject these two
contingents in classification. From these circumstances, and especially
from the undefined objects and criterions of the natural system, the
number of divisions, such as genera, sub-families, families, &c.,
&c., has been quite arbitrary2; without the clearest
definition, how can it be possible to decide whether two groups of
species are of equal value, and of what value? whether they should both
be called genera or families; or whether one should be a genus, and the
other a family3?

1Origin, Ed. i. pp.
419, 427, vi. pp. 575, 582.

2 This is discussed from the
point of view of divergence in the Origin, Ed. i. pp. 420,
421, vi. pp. 576, 577.

3 <Footnote by the author.> I
discuss this because if Quinarism true, I false. <The Quinary System is
set forth in W. S. Macleay's Horæ Entomologicæ, 1821.>

I have only one other remark on the affinities of organic
beings; that is, when two quite distinct groups approach each other,
the approach is generally generic1 and not
special; I can explain this most easily by an example: of all Rodents
the Bizcacha, by certain peculiarities in its reproductive system,
approaches nearest to the Marsupials; of all Marsupials the
Phascolomys, on the other hand, appears to approach in the form of its
teeth and intestines nearest to the Rodents; but there is no special
relation between these two genera2; the Bizcacha is no
nearer related to the Phascolomys than to any other Marsupial in the
points in which it approaches this division; nor again is the
Phascolomys, in the points of structure in which it approaches the
Rodents, any nearer related to the Bizcacha than to any other Rodent.
Other examples might have been chosen, but I have given (from
Waterhouse) this example as it illustrates another point, namely, the
difficulty of determining what are analogical or adaptive and what real
affinities; it seems that the teeth of the Phascolomys though appearing
closely to resemble those of a Rodent are found to be built on
the Marsupial type; and it is thought that these teeth and consequently
the intestines may have been adapted to the peculiar life of this
animal and therefore may not show any real relation. The structure in
the Bizcacha that connects it with the Marsupials does not seem a
peculiarity related to its manner of life, and I imagine that no one
would doubt that this shows a real affinity, though not more with any
one Marsupial

1 In the corresponding passage
in the Origin, Ed. i. p. 430, vi. p. 591, the term general is used in place of generic, and seems a better
expression. In the margin the author gives Waterhouse as his authority.

species than with another. The difficulty of determining
what relations are real and what analogical is far from surprising when
no one pretends to define the meaning of the term relation or the
ulterior object of all classification. We shall immediately see on the
theory of descent how it comes that there should be "real" and
"analogical" affinities; and why the former alone should be of value in
classification—difficulties
which it would be I believe impossible to explain on the ordinary
theory of separate creations.

Classification of Races or
Varieties.

Let us now for a few moments turn to the classification of
the generally acknowledged varieties and subdivisions of our domestic
beings1; we shall find them systematically arranged in
groups of higher and higher value. De Candolle has treated the
varieties of the cabbage exactly as he would have done a natural family
with various divisions and subdivisions. In dogs again we have one main
division which may be called the family of hounds; of these,
there are several (we will call them) genera, such as
blood-hounds, fox-hounds, and harriers; and of each of these we have
different species, as the blood-hound of Cuba and that of
England; and of the latter again we have breeds truly producing their
own kind, which may be called races or varieties. Here we see a
classification practically used which typifies on a lesser scale that
which holds good in nature. But amongst true species in the natural
system and amongst domestic races the number of divisions or groups,
instituted between those most alike and those most unlike, seems to be
quite

1 In a corresponding passage in
the Origin, Ed. i. p. 423, vi. p. 579, the author makes use
of his knowledge of pigeons. The pseudo-genera among dogs are discussed
in Var. under Dom., Ed. ii. vol. I. p. 38.

arbitrary. The number of the forms in both cases seems
practically, whether or not it ought theoretically, to influence the
denomination of groups including them. In both, geographical
distribution has sometimes been used as an aid to classification1;
amongst varieties, I may instance, the cattle of India or the sheep of
Siberia, which from possessing some characters in common permit a
classification of Indian and European cattle, or Siberian and European
sheep. Amongst domestic varieties we have even something very like the
relations of "analogy" or "adaptation2"; thus the common and
Swedish turnip are both artificial varieties which strikingly resemble
each other, and they fill nearly the same end in the economy of the
farm-yard; but although the swede so much more resembles a turnip than
its presumed parent the field cabbage, no one thinks of putting it out
of the cabbages into the turnips. Thus the greyhound and racehorse,
having been selected and trained for extreme fleetness for short
distances, present an analogical resemblance of the same kind, but less
striking as that between the little otter (Marsupial) of Guiana and the
common otter; though these two otters are really less related than
<are> the horse and dog. We are even cautioned by authors treating on
varieties, to follow the natural in contradistinction of an
artificial system and not, for instance, to class two varieties of the
pine-apple3 near each other, because their fruits
accidentally resemble each other closely (though the fruit may be
called the final end of this plant in the economy of its
world, the hot-house), but to judge from the general resemblance of the
entire plants. Lastly, varieties often become extinct; sometimes from
unexplained causes, some-

times from accident, but more often from the production of
more useful varieties, and the less useful ones being destroyed or bred
out.

I think it cannot be doubted that the main cause of all
the varieties which have descended from the aboriginal dog or dogs, or
from the aboriginal wild cabbage, not being equally like or unlike—but
on the contrary, obviously falling into groups and subgroups—must
in chief part be attributed to different degrees of true relationship;
for instance, that the different kinds of blood-hound have descended
from one stock, whilst the harriers have descended from another stock,
and that both these have descended from a different stock from that
which has been the parent of the several kinds of greyhound. We often
hear of a florist having some choice variety and breeding from it a
whole group of sub-varieties more or less characterised by the
peculiarities of the parent. The case of the peach and nectarine, each
with their many varieties, might have been introduced. No doubt the
relationship of our different domestic breeds has been obscured in an
extreme degree by their crossing; and likewise from the slight
difference between many breeds it has probably often happened that a
"sport" from one breed has less closely resembled its parent breed than
some other breed, and has therefore been classed with the latter.
Moreover the effects of a similar climate1 may in some cases
have more than counterbalanced the similarity, consequent on a common
descent, though I should think the similarity of the breeds of cattle
of India or sheep of Siberia was far more probably due to the community
of their descent than to the effects of climate on animals descended
from different stocks.

Notwithstanding these great sources of difficulty,

1 A general statement of the
influence of conditions on variation occurs in the Origin,
Ed. i. pp. 131-3, vi. pp. 164-5.

I apprehend every one would admit, that if it were
possible, a genealogical classification of our domestic varieties would
be the most satisfactory one; and as far as varieties were concerned
would be the natural system: in some cases it has been followed. In
attempting to follow out this object a person would have to class a
variety, whose parentage he did not know, by its external characters;
but he would have a distinct ulterior object in view, namely, its
descent in the same manner as a regular systematist seems also to have
an ulterior but undefined end in all his classifications. Like the
regular systematist he would not care whether his characters were drawn
from more or less important organs as long as he found in the tribe
which he was examining that the characters from such parts were
persistent; thus amongst cattle he does value a character drawn from
the form of the horns more than from the proportions of the limbs and
whole body, for he finds that the shape of the horns is to a
considerable degree persistent amongst cattle1, whilst the
bones of the limbs and body vary. No doubt as a frequent rule the more
important the organ, as being less related to external influences, the
less liable it is to variation; but he would expect that according to
the object for which the races had been selected, parts more or less
important might differ; so that characters drawn from parts generally
most liable to vary, as colour, might in some instances be highly
serviceable—as is the case.
He would admit that general resemblances scarcely definable by language
might sometimes serve to allocate a species by its nearest relation. He
would be able to assign a clear reason why the close similarity of the
fruit in two varieties of pine-apple, and of the so-called root in the
common and Swedish turnips, and why the

1Origin, Ed. i. p.
423, vi. p. 579. In the margin Marshall is given as the authority.

similar gracefulness of form in the greyhound and
racehorse, are characters of little value in classification; namely,
because they are the result, not of community of descent, but either of
selection for a common end, or of the effects of similar external
conditions.

Classification of "races" and species similar.

Thus seeing that both the classifiers of species and of
varieties1 work by the same means, make similar distinctions
in the value of the characters, and meet with similar difficulties, and
that both seem to have in their classification an ulterior object in
view; I cannot avoid strongly suspecting that the same cause, which has
made amongst our domestic varieties groups and sub-groups, has made
similar groups (but of higher values) amongst species; and that this
cause is the greater or less propinquity of actual descent. The simple
fact of species, both those long since extinct and those now living,
being divisible into genera, families, orders &c.—divisions
analogous to those into which varieties are divisible—is
otherwise an inexplicable fact, and only not remarkable from its
familiarity.

Origin of genera and
families.

Let us suppose2 for example that a species
spreads and arrives at six or more different regions, or being already
diffused over one wide area, let this area be divided into six distinct
regions, exposed to different conditions, and with stations slightly
different, not fully occupied with other species, so

1Origin, Ed. i. p.
423, vi. p. 579.

2 The discussion here following
corresponds more or less to the Origin, Ed. i. pp. 411, 412,
vi. pp. 566, 567; although the doctrine of divergence is not mentioned
in this Essay (as it is in the Origin) yet the present
section seems to me a distinct approximation to it.

that six different races or species were formed by
selection, each best fitted to its new habits and station. I must
remark that in every case, if a species becomes modified in any one
sub-region, it is probable that it will become modified in some other
of the sub-regions over which it is diffused, for its organization is
shown to be capable of being rendered plastic; its diffusion proves
that it is able to struggle with the other inhabitants of the several
sub-regions; and as the organic beings of every great region are in
some degree allied, and as even the physical conditions are often in
some respects alike, we might expect that a modification in structure,
which gave our species some advantage over antagonist species in one
sub-region, would be followed by other modifications in other of the
sub-regions. The races or new species supposed to be formed would be
closely related to each other; and would either form a new genus or
sub-genus, or would rank (probably forming a slightly different
section) in the genus to which the parent species belonged. In the
course of ages, and during the contingent physical changes, it is
probable that some of the six new species would be destroyed; but the
same advantage, whatever it may have been (whether mere tendency to
vary, or some peculiarity of organization, power of mind, or means of
distribution), which in the parent-species and in its six selected and
changed species-offspring, caused them to prevail over other antagonist
species, would generally tend to preserve some or many of them for a
long period. If then, two or three of the six species were preserved,
they in their turn would, during continued changes, give rise to as
many small groups of species: if the parents of these small groups were
closely similar, the new species would form one great genus, barely
perhaps divisible into two or three sections: but if the

parents were considerably unlike, their species-offspring
would, from inheriting most of the peculiarities of their
parent-stocks, form either two or more sub-genera or (if the course of
selection tended in different ways) genera. And lastly species
descending from different species of the newly formed genera would form
new genera, and such genera collectively would form a family.

The extermination of species follows from changes in the
external conditions, and from the increase or immigration of more
favoured species: and as those species which are undergoing
modification in any one great region (or indeed over the world) will
very often be allied ones from (as just explained) partaking of many
characters, and therefore advantages in common, so the species, whose
place the new or more favoured ones are seizing, from partaking of a
common inferiority (whether in any particular point of structure, or of
general powers of mind, of means of distribution, of capacity for
variation, &c., &c.), will be apt to be allied. Consequently
species of the same genus will slowly, one after the other, tend to
become rarer and rarer in numbers, and finally extinct; and as each
last species of several allied genera fails, even the family will
become extinct. There may of course be occasional exceptions to the
entire destruction of any genus or family. From what has gone before,
we have seen that the slow and successive formation of several new
species from the same stock will make a new genus, and the slow and
successive formation of several other new species from another stock
will make another genus; and if these two stocks were allied, such
genera will make a new family. Now, as far as our knowledge serves, it
is in this slow and gradual manner that groups of species appear on,
and disappear from, the face of the earth.

The manner in which, according to our theory, the
arrangement of species in groups is due to partial extinction, will
perhaps be rendered clearer in the following way. Let us suppose in any
one great class, for instance in the Mammalia, that every species and
every variety, during each successive age, had sent down one unaltered
descendant (either fossil or living) to the present time; we should
then have had one enormous series, including by small gradations every
known mammiferous form; and consequently the existence of groups1,
or chasms in the series, which in some parts are in greater width, and
in some of less, is solely due to former species, and whole groups of
species, not having thus sent down descendants to the present time.

With respect to the "analogical" or "adaptive"
resemblances between organic beings which are not really related2,
I will only add, that probably the isolation of different groups of
species is an important element in the production of such characters:
thus we can easily see, in a large increasing island, or even a
continent like Australia, stocked with only certain orders of the main
classes, that the conditions would be highly favourable for species
from these orders to become adapted to play parts in the economy of
nature, which in other countries were performed by tribes especially
adapted to such parts. We can understand how it might happen that an
otter-like animal might have been formed in Australia by slow selection
from the more carnivorous Marsupial types; thus we can understand that
curious case in the southern hemisphere, where there are no auks (but
many petrels), of a petrel3 having been modified into the

external general form so as to play the same office in
nature with the auks of the northern hemisphere; although the habits
and form of the petrels and auks are normally so wholly different. It
follows, from our theory, that two orders must have descended from one
common stock at an immensely remote epoch; and we can perceive when a
species in either order, or in both, shows some affinity to the other
order, why the affinity is usually generic and not particular—that
is why the Bizcacha amongst Rodents, in the points in which it is
related to the Marsupial, is related to the whole group1,
and not particularly to the Phascolomys, which of all Marsupialia is
related most to the Rodents. For the Bizcacha is related to the present
Marsupialia, only from being related to their common parent-stock; and
not to any one species in particular. And generally, it may be observed
in the writings of most naturalists, that when an organism is described
as intermediate between two great groups, its relations are
not to particular species of either group, but to both groups, as
wholes. A little reflection will show how exceptions (as that of the
Lepidosiren, a fish closely related to particular reptiles)
might occur, namely from a few descendants of those species, which at a
very early period branched out from a common parent-stock and so formed
the two orders or groups, having survived, in nearly their original
state, to the present time.

Finally, then, we see that all the leading facts in the
affinities and classification of organic beings can be explained on the
theory of the natural system being simply a genealogical one. The
similarity of the principles in classifying domestic varieties and true
species, both those living and extinct, is at once

explained; the rules followed and difficulties met with
being the same. The existence of genera, families, orders, &c., and
their mutual relations, naturally ensues from extinction going on at
all periods amongst the diverging descendants of a common stock. These
terms of affinity, relations, families, adaptive characters, &c.,
which naturalists cannot avoid using, though metaphorically, cease
being so, and are full of plain signification.

SCARCELY anything is more wonderful or has been oftener
insisted on than that the organic beings in each great class, though
living in the most distant climes and at periods immensely remote,
though fitted to widely different ends in the economy of nature, yet
all in their internal structure evince an obvious uniformity. What, for
instance, is more wonderful than that the hand to clasp, the foot or
hoof to walk, the bat's wing to fly, the porpoise's fin2 to
swim, should all be built on the same plan? and that the bones in their
position and number should be so similar that they can all be classed
and called by the same names. Occasionally some of the bones are merely
represented by an apparently useless, smooth style, or are soldered
closely to other bones, but the unity of type is not by this destroyed,
and hardly rendered less clear. We see in this fact some deep bond of
union between the organic beings of the same great classes—to
illustrate which is the object and foundation of the natural

2Origin, Ed. i. p.
434, vi. p. 596. In the Origin, Ed. i. these examples occur
under the heading Morphology, the author does not there draw
much distinction between this heading and that of Unity of Type.

system. The perception of this bond, I may add, is the
evident cause that naturalists make an ill-defined distinction between
true and adaptive affinities.

Morphology.

There is another allied or rather almost identical class
of facts admitted by the least visionary naturalists and included under
the name of Morphology. These facts show that in an individual organic
being, several of its organs consist of some other organ metamorphosed1:
thus the sepals, petals, stamens, pistils, &c. of every plant can
be shown to be metamorphosed leaves; and thus not only can the number,
position and transitional states of these several organs, but likewise
their monstrous changes, be most lucidly explained. It is believed that
the same laws hold good with the gemmiferous vesicles of Zoophytes. In
the same manner the number and position of the extraordinarily
complicated jaws and palpi of Crustacea and of insects, and likewise
their differences in the different groups, all become simple, on the
view of these parts, or rather legs and all metamorphosed appendages,
being metamorphosed legs. The skulls, again, of the Vertebrata are
composed of three metamorphosed vertebræ, and thus we can see a meaning
in the number and strange complication of the bony case of the brain.
In this latter instance, and in that of the jaws of the Crustacea, it
is only necessary to see a series taken from the different groups of
each class to admit the truth of these views. It is evident that when
in each species of a group its organs consist of some other part
metamorphosed, that there must also be a "unity of type" in such a
group. And

1 See Origin, Ed. i.
p. 436, vi. p. 599, where the parts of the flower, the jaws and palpi
of Crustaceans and the vertebrate skull are given as examples.

in the cases as that above given in which the foot, hand,
wing and paddle are said to be constructed on a uniform type, if we
could perceive in such parts or organs traces of an apparent change
from some other use or function, we should strictly include such parts
or organs in the department of morphology: thus if we could trace in
the limbs of the Vertebrata, as we can in their ribs, traces of an
apparent change from being processes of the vertebræ, it would be said
that in each species of the Vertebrata the limbs were "metamorphosed
spinal processes," and that in all the species throughout the class the
limbs displayed a "unity of type1."

These wonderful parts of the hoof, foot, hand, wing,
paddle, both in living and extinct animals, being all constructed on
the same framework, and again of the petals, stamina, germens, &c.
being metamorphosed leaves, can by the creationist be viewed only as
ultimate facts and incapable of explanation; whilst on our theory of
descent these facts all necessary follow: for by this theory all the
beings of any one class, say of the mammalia, are supposed to be
descended from one parent-stock, and to have been altered by such
slight steps as man effects by the selection of chance domestic
variations. Now we can see according to this view that a foot might be
selected with longer and longer bones, and wider connecting membranes,
till it became a swimming organ, and so on till it became an organ by
which to flap along the surface or to glide over it, and lastly to fly
through the air: but in such changes there would be no tendency to
alter the framework of the internal inherited structure. Parts might
become lost (as the tail in dogs, or horns in cattle, or the pistils in
plants), others might become united together (as in the feet of the

Lincolnshire breed of pigs1, and in the stamens
of many garden flowers); parts of a similar nature might become
increased in number (as the vertebræ in the tails of pigs, &c.,
&c. and the fingers and toes in six-fingered races of men and in
the Dorking fowls), but analogous differences are observed in nature
and are not considered by naturalists to destroy the uniformity of the
types. We can, however, conceive such changes to be carried to such
length that the unity of type might be obscured and finally be
undistinguishable, and the paddle of the Plesiosaurus has been advanced
as an instance in which the uniformity of type can hardly be recognised2.
If after long and gradual changes in the structure of the
co-descendants from any parent stock, evidence (either from
monstrosities or from a graduated series) could be still detected of
the function, which certain parts or organs played in the parent stock,
these parts or organs might be strictly determined by their former
function with the term "metamorphosed" appended. Naturalists have used
this term in the same metaphorical manner as they have been obliged to
use the terms of affinity and relation; and when they affirm, for
instance, that the jaws of a crab are metamorphosed legs, so that one
crab has more legs and fewer jaws than another, they are far from
meaning that the jaws, either during the life of the individual crab or
of its progenitors, were really legs. By our theory this term assumes
its literal meaning3; and this wonderful fact of the complex
jaws of an animal

1 The solid-hoofed pigs
mentioned in Var. under Dom., Ed. ii. vol. II.
p. 424 are not Lincolnshire pigs. For other cases see
Bateson, Materials for the Study of Variation, 1894, pp.
387-90.

2 In the margin C. Bell is given
as authority, apparently for the statement about Plesiosaurus. See Origin, Ed. i. p. 436, vi p. 598, where the author speaks of the "general
pattern" being obscured in "extinct gigantic sea lizards." In the same
place the suctorial Entomostraca are added as examples of the
difficulty of recognising the type.

retaining numerous characters, which they would probably
have retained if they had really been metamorphosed during many
successive generations from true legs, is simply explained.

Embryology.

The unity of type in the great classes is shown in another
and very striking manner, namely, in the stages through which the
embryo passes in coming to maturity1. Thus, for instance, at
one period of the embryo, the wings of the bat, the hand, hoof or foot
of the quadruped, and the fin of the porpoise do not differ, but
consist of a simple undivided bone. At a still earlier period the
embryo of the fish, bird, reptile and mammal all strikingly resemble
each other. Let it not be supposed this resemblance is only external;
for on dissection, the arteries are found to branch out and run in a
peculiar course, wholly unlike that in the full-grown mammal and bird,
but much less unlike that in the full-grown fish, for they run as if to
ærate blood by branchiæ2 on the neck, of which even the
slit-like orifices can be discerned. How wonderful it is that this
structure should be present in the embryos of animals about to be
developed into such different forms, and of which two great classes
respire only in the air. Moreover, as the embryo of the mammal is
matured in the parent's body, and that of the bird in an egg in the
air, and that of the fish in an egg in the water, we cannot believe
that this course of the arteries is related to any external conditions.
In all shell-fish (Gasteropods) the embryo passes through a state
analogous to that of the Pteropodous Mol-

1Origin, Ed. i. p.
439, vi. p. 604.

2 The uselessness of the
branchial arches in mammalia is insisted on in the Origin,
Ed. i. p. 440, vi. p. 606. Also the uselessness of the spots on the
young blackbird and the stripes of the lion-whelp, cases which do not
occur in the present Essay.

lusca: amongst insects again, even the most different
ones, as the moth, fly and beetle, the crawling larvæ are all closely
analogous: amongst the Radiata, the jelly-fish in its embryonic state
resembles a polype, and in a still earlier state an infusorial
animalcule—as does likewise
the embryo of the polype. From the part of the embryo of a mammal, at
one period, resembling a fish more than its parent form; from the larvæ
of all orders of insects more resembling the simpler articulate animals
than their parent insects1; and from such other cases as the
embryo of the jelly-fish resembling a polype much nearer than the
perfect jelly-fish; it has often been asserted that the higher animal
in each class passes through the state of a lower animal; for instance,
that the mammal amongst the vertebrata passes through the state of a
fish2: but Müller denies this, and affirms that the young
mammal is at no time a fish, as does Owen assert that the embryonic
jelly-fish is at no time a polype, but that mammal and fish, jelly-fish
and polype pass through the same state; the mammal and jelly-fish being
only further developed or changed.

As the embryo, in most cases, possesses a less complicated
structure than that into which it is to be developed, it might have
been thought that the resemblance of the embryo to less complicated
forms in the same great class, was in some manner a necessary
preparation for its higher development; but in fact the embryo, during
its growth, may become less, as well as more, complicated3.
Thus certain female Epizoic Crustaceans in their mature

1 In the Origin, Ed.
i. pp. 442, 448, vi. pp. 608, 614 it is pointed out that in some cases
the young form resembles the adult, e.g. in spiders; again,
that in the Aphis there is no "worm-like stage" of development.

state have neither eyes nor any organs of locomotion; they
consist of a mere sack, with a simple apparatus for digestion and
procreation; and when once attached to the body of the fish, on which
they prey, they never move again during their whole lives: in their
embryonic condition, on the other hand, they are furnished with eyes,
and with well articulated limbs, actively swim about and seek their
proper object to become attached to. The larvæ, also, of some moths are
as complicated and are more active than the wingless and limbless
females, which never leave their pupa-case, never feed and never see
the daylight.

Attempt to explain the
facts of embryology.

I think considerable light can be thrown by the theory of
descent on these wonderful embryological facts which are common in a
greater or less degree to the whole animal kingdom, and in some manner
to the vegetable kingdom: on the fact, for instance, of the arteries in
the embryonic mammal, bird, reptile and fish, running and branching in
the same courses and nearly in the same manner with the arteries in the
full-grown fish; on the fact I may add of the high importance to
systematic naturalists1 of the characters and resemblances
in the embryonic state, in ascertaining the true position in the
natural system of mature organic beings. The following are the
considerations which throw light on these curious points.

In the economy, we will say of a feline animal2,
the feline structure of the embryo or of the sucking kitten is of quite
secondary importance to it; hence, if a feline animal varied (assuming
for the time the

1Origin, Ed. i. p.
449, vi. p. 617.

2 This corresponds to the Origin, Ed. i. pp. 443-4, vi. p. 610: the "feline animal" is not used to
illustrate the generalisation, but is so used in the Essay of 1842, p.
42.

possibility of this) and if some place in the economy of
nature favoured the selection of a longer-limbed variety, it would be
quite unimportant to the production by natural selection of a
long-limbed breed, whether the limbs of the embryo and kitten were
elongated if they became so as soon as the animal
had to provide food for itself. And if it were found after continued
selection and the production of several new breeds from one
parent-stock, that the successive variations had supervened, not very
early in the youth or embryonic life of each breed (and we have just
seen that it is quite unimportant whether it does so or not), then it
obviously follows that the young or embryos of the several breeds will
continue resembling each other more closely than their adult parents1.
And again, if two of these breeds became each the parent-stock of
several other breeds, forming two genera, the young and embryos of
these would still retain a greater resemblance to the one original
stock than when in an adult state. Therefore if it could be shown that
the period of the slight successive variations does not always
supervene at a very early period of life, the greater resemblance or
closer unity in type of animals in the young than in the full-grown
state would be explained. Before practically2 endeavouring
to discover in our domestic races whether the structure or form of the
young has or has not changed in an exactly corresponding degree with
the changes of full-grown animals, it will be well to show that it is
at least quite possible for the primary germinal vesicle to
be impressed with a tendency to produce some change on the growing
tissues which will not be fully effected till the animal is advanced in
life.

1Origin, Ed. i p.
447, vi. p. 613.

2 In the margin is written "Get
young pigeons"; this was afterwards done, and the results are given in
the Origin, Ed. i. p. 445, vi. p. 612.

From the following peculiarities of structure being
inheritable and appearing only when the animal is full-grown—namely,
general size, tallness (not consequent on the tallness of the infant),
fatness either over the whole body, or local; change of colour in hair
and its loss; deposition of bony matter on the legs of horses;
blindness and deafness, that is changes of structure in the eye and
ear; gout and consequent deposition of chalk-stones; and many other
diseases1, as of the heart and brain, &c., &c.; from
all such tendencies being I repeat inheritable, we clearly see that the
germinal vesicle is impressed with some power which is wonderfully
preserved during the production of infinitely numerous cells in the
ever changing tissues, till the part ultimately to be affected is
formed and the time of life arrived at. We see this clearly when we
select cattle with any peculiarity of their horns, or poultry with any
peculiarity of their second plumage, for such peculiarities cannot of
course reappear till the animal is mature. Hence, it is certainly possible that the germinal vesicle may be impressed with a tendency to
produce a long-limbed animal, the full proportional length of whose
limbs shall appear only when the animal is mature2.

In several of the cases just enumerated we know that the
first cause of the peculiarity, when not inherited, lies in
the conditions to which the animal is exposed during mature life, thus
to a certain extent general size and fatness, lameness in horses and in
a lesser degree blindness, gout and some other diseases are certainly
in some degree caused

1 In the Origin, Ed.
i. the corresponding passages are at pp. 8, 13, 443, vi. pp. 8, 15,
610. In the Origin, Ed. i. I have not found a passage so
striking as that which occurs a few lines lower "that the germinal
vesicle is impressed with some power which is wonderfully preserved,
&c." In the Origin this preservation is
rather taken for granted.

2 <In the margin is written>
Aborted organs show, perhaps, something about period <at> which changes
supervene in embryo.

and accelerated by the habits of life, and these
peculiarities when transmitted to the offspring of the affected person
reappear at a nearly corresponding time of life. In medical works it is
asserted generally that at whatever period an hereditary disease
appears in the parent, it tends to reappear in the offspring at the
same period. Again, we find that early maturity, the season of
reproduction and longevity are transmitted to corresponding periods of
life. Dr Holland has insisted much on children of the same family
exhibiting certain diseases in similar and peculiar manners; my father
has known three brothers1 die in very old age in a singular comatose state; now to make these latter cases strictly bear, the
children of such families ought similarly to suffer at corresponding
times of life; this is probably not the case, but such facts show that
a tendency in a disease to appear at particular stages of life can be
transmitted through the germinal vesicle to different individuals of
the same family. It is then certainly possible that diseases affecting
widely different periods of life can be transmitted. So little
attention is paid to very young domestic animals that I do not know
whether any case is on record of selected peculiarities in young
animals, for instance, in the first plumage of birds, being transmitted
to their young. If, however, we turn to silk-worms2, we find
that the caterpillars and coccoons (which must correspond to a very
early period of the embryonic life of mammalia) vary, and that
these varieties reappear in the offspring caterpillars and coccoons.

I think these facts are sufficient to render it probable
that at whatever period of life any peculiarity (capable of being
inherited) appears, whether caused by the action of external influences

during mature life, or from an affection of the primary
germinal vesicle, it tends to reappear in the offspring at
the corresponding period of life1. Hence (I may add)
whatever effect training, that is the full employment or action of
every newly selected slight variation, has in fully developing and
increasing such variation, would only show itself in mature age,
corresponding to the period of training; in the second chapter I showed
that there was in this respect a marked difference in natural and
artificial selection, man not regularly exercising or adapting his
varieties to new ends, whereas selection by nature presupposes such
exercise and adaptation in each selected and changed part. The
foregoing facts show and presuppose that slight variations occur at
various periods of life after birth; the facts of
monstrosity, on the other hand, show that many changes take place
before birth, for instance, all such cases as extra fingers, hare-lip
and all sudden and great alterations in structure; and these when
inherited reappear during the embryonic period in the offspring. I will
only add that at a period even anterior to embryonic life, namely,
during the egg state, varieties appear in size and colour (as with the
Hertfordshire duck with blackish eggs2) which reappear in
the egg; in plants also the capsule and membranes of the seed are very
variable and inheritable.

If then the two following propositions are admitted (and I
think the first can hardly be doubted), viz. that variation of
structure takes place at all times of life, though no doubt far less in
amount and seldomer in quite mature life3 (and then generally

1Origin, Ed. i. p.
444, vi. p. 610.

2 In Var. under Dom.,
Ed. ii. vol. I. p. 295, such eggs are said to be laid
early in each season by the black Labrador duck. In the next sentence
in the text the author does not distinguish the characters of the
vegetable capsule from those of the ovum.

3 This seems to me to be more
strongly stated here than in the Origin, Ed. i.

taking the form of disease); and secondly, that these
variations tend to reappear at a corresponding period of life, which
seems at least probable, then we might a priori have
expected that in any selected breed the young animal would
not partake in a corresponding degree the peculiarities characterising
the full-grown parent; though it would in a lesser degree.
For during the thousand or ten thousand selections of slight increments
in the length of the limbs of individuals necessary to produce a
long-limbed breed, we might expect that such increments would take
place in different individuals (as we do not certainly know at what
period they do take place), some earlier and some later in the
embryonic state, and some during early youth; and these increments
would reappear in their offspring only at corresponding periods. Hence,
the entire length of limb in the new long-limbed breed would only be
acquired at the latest period of life, when that one which was latest
of the thousand primary increments of length supervened. Consequently,
the fœtus of the new breed during the earlier part of its existence
would remain much less changed in the proportions of its limbs; and the
earlier the period the less would the change be.

Whatever may be thought of the facts on which this
reasoning is grounded, it shows how the embryos and young of different
species might come to remain less changed than their mature parents;
and practically we find that the young of our domestic animals, though
differing, differ less than their full-grown, parents. Thus if we look
at the young puppies1 of the greyhound and bulldog—(the
two most obviously modified of the breeds of dog)—we
find their puppies at the age of six days with legs and noses (the
latter measured from the eyes to the tip) of the1Origin, Ed. i. p. 444, vi. p. 611.

same length; though in the proportional thicknesses and
general appearance of these parts there is a great difference. So it is
with cattle, though the young calves of different breeds are easily
recognisable, yet they do not differ so much in their proportions as
the full-grown animals. We see this clearly in the fact that it shows
the highest skill to select the best forms early in life, either in
horses, cattle or poultry; no one would attempt it only a few hours
after birth; and it requires great discrimination to judge with
accuracy even during their full youth, and the best judges are
sometimes deceived. This shows that the ultimate proportions of the
body are not acquired till near mature age. If I had collected
sufficient facts to firmly establish the proposition that in
artificially selected breeds the embryonic and young animals are not
changed in a corresponding degree with their mature parents, I might
have omitted all the foregoing reasoning and the attempts to explain
how this happens; for we might safely have transferred the proposition
to the breeds or species naturally selected; and the ultimate effect
would necessarily have been that in a number of races or species
descended from a common stock and forming several genera and families
the embryos would have resembled each other more closely than
full-grown animals. Whatever may have been the form or habits of the
parent-stock of the Vertebrata, in whatever course the arteries ran and
branched, the selection of variations, supervening after the first
formation of the arteries in the embryo, would not tend from variations
supervening at corresponding periods to alter their course at that
period: hence, the similar course of the arteries in the mammal, bird,
reptile and fish, must be looked at as a most ancient record of the
embryonic structure of the common parent-stock of these four great
classes.

A long course of selection might cause a form to become
more simple, as well as more complicated; thus the adaptation of a
crustaceous1 animal to live attached during its whole life
to the body of a fish, might permit with advantage great simplification
of structure, and on this view the singular fact of an embryo being
more complex than its parent is at once explained.

On the graduated
complexity in each great class.

I may take this opportunity of remarking that naturalists
have observed that in most of the great classes a series exists from
very complicated to very simple beings; thus in Fish, what a range
there is between the sand-eel and shark,—in the Articulata, between the
common crab and the Daphnia2,—between the Aphis and
butterfly, and between a mite and a spider3. Now the
observation just made, namely, that selection might tend to simplify,
as well as to complicate, explains this; for we can see that during the
endless geologico-geographical changes, and consequent isolation of
species, a station occupied in other districts by less complicated
animals might be left unfilled, and be occupied by a degraded form of a
higher or more complicated class; and it would by no means follow that,
when the two regions became united, the degraded organism would give
way to the aboriginally lower organism. According to our theory, there
is obviously no power tending constantly to exalt species, except the
mutual struggle between the different individuals and classes; but from
the strong and general hereditary tendency we might expect to find some
tendency to progressive complication in the successive production of
new organic forms.

1Origin, Ed. i. p.
441, vi. p. 607.

2 Compare Origin, Ed.
i. p. 419, vi. p. 575.

3 <Note in original.> Scarcely
possible to distinguish between non-development and retrograde
development.

Ihave above remarked that the
feline1 form is quite of secondary importance to the embryo
and to the kitten. Of course, during any great and prolonged change of
structure in the mature animal, it might, and often would be,
indispensable that the form of the embryo should be changed; and this
could be effected, owing to the hereditary tendency at corresponding
ages, by selection, equally well as in mature age: thus if the embryo
tended to become, or to remain, either over its whole body or in
certain parts, too bulky, the female parent would die or suffer more
during parturition; and as in the case of the calves with large hinder
quarters2, the peculiarity must be either eliminated or the
species become extinct. Where an embryonic form has to seek its own
food, its structure and adaptation is just as important to the species
as that of the full-grown animal; and as we have seen that a
peculiarity appearing in a caterpillar (or in a child, as shown by the
hereditariness of peculiarities in the milk-teeth) reappears in its
offspring, so we can at once see that our common principle of the
selection of slight accidental variations would modify and adapt a
caterpillar to a new or changing condition, precisely as in the
full-grown butterfly. Hence probably it is that caterpillars of
different species of the Lepidoptera differ more than those embryos, at
a corresponding early period of life, do which remain inactive in the
womb of their parents. The parent during successive ages continuing to
be adapted by selection for some one object, and the larva for quite
another one, we need not wonder at

the difference becoming wonderfully great between them;
even as great as that between the fixed rock-barnacle and its free,
crab-like offspring, which is furnished with eyes and well-articulated,
locomotive limbs1.

Importance of embryology
in classification.

We are now prepared to perceive why the study of embryonic
forms is of such acknowledged importance in classification2.
For we have seen that a variation, supervening at any time, may aid in
the modification and adaptation of the full-grown being; but for the
modification of the embryo, only the variations which supervene at a
very early period can be seized on and perpetuated by selection: hence
there will be less power and less tendency (for the structure of the
embryo is mostly unimportant) to modify the young: and hence we might
expect to find at this period similarities preserved between different
groups of species which had been obscured and quite lost in the
full-grown animals. I conceive on the view of separate creations it
would be impossible to offer any explanation of the affinities of
organic beings thus being plainest and of the greatest importance at
that period of life when their structure is not adapted to the final
part they have to play in the economy of nature.

Order in time in which the
great classes have first
appeared.

It follows strictly from the above reasoning only that the
embryos of (for instance) existing vertebrata resemble more closely the
embryo of the parent-stock of this great class than do full-grown
existing vertebrata resemble their full-grown parent-

stock. But it may be argued with much probability that in
the earliest and simplest condition of things the parent and embryo
must have resembled each other, and that the passage of any animal
through embryonic states in its growth is entirely due to subsequent
variations affecting only the more mature periods of life.
If so, the embryos of the existing vertebrata will shadow forth the
full-grown structure of some of those forms of this great class which
existed at the earlier periods of the earth's history1: and
accordingly, animals with a fish-like structure ought to have preceded
birds and mammals; and of fish, that higher organized division with the
vertebræ extending into one division of the tail ought to have
preceded the equal-tailed, because the embryos of the latter have an
unequal tail; and of Crustacea, entomostraca ought to have preceded the
ordinary crabs and barnacles—polypes
ought to have preceded jelly-fish,
and infusorial animalcules to have existed before both. This order of
precedence in time in some of these cases is believed to hold good; but
I think our evidence is so exceedingly incomplete regarding the number
and kinds of organisms which have existed during all, especially the
earlier, periods of the earth's history, that I should put no stress on
this accordance, even if it held truer than it probably does in our
present state of knowledge.

PARTS of structure are said to be "abortive," or when in a
still lower state of development "rudimentary1," when the
same reasoning power, which convinces us that in some cases similar
parts are beautifully adapted to certain ends, declares that in others
they are absolutely useless. Thus the rhinoceros, the whale2,
etc., have, when young, small but properly formed teeth, which never
protrude from the jaws; certain bones, and even the entire extremities
are represented by mere little cylinders or points of bone, often
soldered to other bones: many beetles have exceedingly minute but
regularly formed wings lying under their wing-cases3, which
latter are united never to be opened: many plants have, instead of
stamens, mere filaments or little knobs; petals are reduced to scales,
and whole flowers to buds, which (as in the feather hyacinth) never
expand. Similar instances are almost innumerable, and are justly
considered wonderful: probably not one organic being exists in which
some part does not bear the stamp of inutility; for what can be clearer4,
as far as our reasoning powers

1 In the Origin, Ed.
i. p. 450, vi. p. 619, the author does not lay stress on any
distinction in meaning between the terms abortive and rudimentary organs.

can reach, than that teeth are for eating, extremities for
locomotion, wings for flight, stamens and the entire flower for
reproduction; yet for these clear ends the parts in question are
manifestly unfit. Abortive organs are often said to be mere
representatives (a metaphorical expression) of similar parts in other
organic beings; but in some cases they are more than representatives,
for they seem to be the actual organ not fully grown or developed; thus
the existence of mammæ in the male vertebrata is one of the oftenest
adduced cases of abortion; but we know that these organs in man (and in
the bull) have performed their proper function and secreted milk: the
cow has normally four mammæ and two abortive ones, but these latter in
some instances are largely developed and even (??) give milk1.
Again in flowers, the representatives of stamens and pistils can be
traced to be really these parts not developed; Kölreuter has shown by
crossing a diæcious plant (a Cucubalus) having a rudimentary pistil2 with another species having this organ perfect, that in the hybrid
offspring the rudimentary part is more developed, though still
remaining abortive; now this shows how intimately related in nature the
mere rudiment and the fully developed pistil must be.

Abortive organs, which must be considered as useless as
far as their ordinary and normal purpose is concerned, are sometimes
adapted to other ends3: thus the marsupial bones, which
properly serve to support the young in the mother's pouch, are present
in the male and serve as the fulcrum for muscles connected only with
male functions: in the

1Origin, Ed. i. p.
451, vi. p. 619, on male mammæ. In the Origin he speaks
certainly of the abortive mammæ of the cow giving milk,—a point which
is here queried.

2Origin, Ed. i. p.
451, vi p. 620.

3 The care of rudimentary organs
adapted to new purposes is discussed in the Origin, Ed. i. p.
451, vi. p. 620.

male of the marigold flower the pistil is abortive for its
proper end of being impregnated, but serves to sweep the pollen out of
the anthers1 ready to be borne by insects to the perfect
pistils in the other florets. It is likely in many cases, yet unknown
to us, that abortive organs perform some useful function; but in other
cases, for instance in that of teeth embedded in the solid jaw-bone, or
of mere knobs, the rudiments of stamens and pistils, the boldest
imagination will hardly venture to ascribe to them any function.
Abortive parts, even when wholly useless to the individual species, are
of great signification in the system of nature; for they are often
found to be of very high importance in a natural classification2;
thus the presence and position of entire abortive flowers, in the
grasses, cannot be overlooked in attempting to arrange them according
to their true affinities. This corroborates a statement in a previous
chapter, viz. that the physiological importance of a part is no index
of its importance in classification. Finally, abortive organs often are
only developed, proportionally with other parts, in the embryonic or
young state of each species3; this again, especially
considering the classificatory importance of abortive organs, is
evidently part of the law (stated in the last chapter) that the higher
affinities of organisms are often best seen in the stages towards
maturity, through which the embryo passes. On the ordinary view of
individual creations, I think that scarcely any class of facts in
natural history are more wonderful or less capable of receiving
explanation.

1 This is here stated on the
authority of Sprengel; see also Origin, Ed. i. p. 452, vi. p.
621.

2Origin, Ed. i. p.
455, vi. p. 627. In the margin R. Brown's name is given apparently as
the authority for the fact.

Physiologists and medical men apply the term "abortive" in
a somewhat different sense from naturalists; and their application is
probably the primary one; namely, to parts, which from accident or
disease before birth are not developed or do not grow1:
thus, when a young animal is born with a little stump in the place of a
finger or of the whole extremity, or with a little button instead of a
head, or with a mere bead of bony matter instead of a tooth, or with a
stump instead of a tail, these parts are said to be aborted.
Naturalists on the other hand, as we have seen, apply this term to
parts not stunted during the growth of the embryo, but which are as
regularly produced in successive generations as any other most
essential parts of the structure of the individual: naturalists,
therefore, use this term in a metaphorical sense. These two classes of
facts, however, blend into each other2; by parts
accidentally aborted, during the embryonic life of one individual,
becoming hereditary in the succeeding generations: thus a cat or dog,
born with a stump instead of a tail, tends to transmit stumps to their
offspring; and so it is with stumps representing the extremities; and
so again with flowers, with defective and rudimentary parts, which are
annually produced in new flower-buds and even in successive seedlings.
The strong hereditary tendency to reproduce every either congenital or
slowly acquired structure, whether useful or injurious to the
individual, has been shown in the first part; so that we need feel no
surprise at these truly abortive

1Origin, Ed. i. p.
454, vi. p. 625.

2 In the Origin, Ed.
i. p. 454, vi. p. 625, the author in referring to semi-monstrous
variations adds "But I doubt whether any of these cases throw light on
the origin of rudimentary organs in a state of nature." In 1844 he was
clearly more inclined to an opposite opinion.

parts becoming hereditary. A curious instance of the force
of hereditariness is sometimes seen in two little loose hanging horns,
quite useless as far as the function of a horn is concerned, which are
produced in hornless races of our domestic cattle1. Now I
believe no real distinction can be drawn between a stump representing a
tail or a horn or the extremities; or a short shrivelled stamen without
any pollen; or a dimple in a petal representing a nectary, when such
rudiments are regularly reproduced in a race or family, and the true
abortive organs of naturalists. And if we had reason to believe (which
I think we have not) that all abortive organs had been at some period suddenly produced during the embryonic life of an individual, and
afterwards become inherited, we should at once have a simple
explanation of the origin of abortive and rudimentary organs2.
In the same manner as during changes of pronunciation certain letters
in a word may become useless3 in pronouncing it, but yet may
aid us in searching for its derivation, so we can see that rudimentary
organs, no longer useful to the individual, may be of high importance
in ascertaining its descent, that is, its true classification in the
natural system.

Abortion from gradual
disuse.

There seems to be some probability that continued disuse
of any part or organ, and the selection of individuals with such parts
slightly less developed, would in the course of ages produce in

1Origin, Ed. i. p.
454, vi. p. 625.

2 See Origin, Ed. i.
p. 454, vi. p. 625. The author there discusses monstrosities in
relation to rudimentary organs, and comes to the conclusion that disuse
is of more importance, giving as a reason his doubt "whether species
under nature ever undergo abrupt changes." It seems to me that in the Origin he gives more weight to the "Lamarckian factor" than he did in
1844. Huxley took the opposite view, see the Introduction.

organic beings under domesticity races with such parts
abortive. We have every reason to believe that every part and organ in
an individual becomes fully developed only with exercise of its
functions; that it becomes developed in a somewhat lesser degree with
less exercise; and if forcibly precluded from all action, such part
will often become atrophied. Every peculiarity, let it be remembered,
tends, especially where both parents have it, to be inherited. The less
power of flight in the common duck compared with the wild, must be
partly attributed to disuse1 during successive generations,
and as the wing is properly adapted to flight, we must consider our
domestic duck in the first stage towards the state of the Aptéryx, in
which the wings are so curiously abortive. Some naturalists have
attributed (and possibly with truth) the falling ears so characteristic
of most domestic dogs, some rabbits, oxen, cats, goats, horses,
&c., &c., as the effects of the lesser use of the muscles of
these flexible parts during successive generations of inactive life;
and muscles, which cannot perform their functions, must be considered
verging towards abortion. In flowers, again, we see the gradual
abortion during successive seedlings (though this is more properly a
conversion) of stamens into imperfect petals, and finally into perfect
petals. When the eye is blinded in early life the optic nerve sometimes
becomes atrophied; may we not believe that where this organ, as is the
case with the subterranean mole-like Tuco-tuco <Ctenomys>2,
is frequently impaired and lost, that in the course of generations the
whole organ might become abortive, as it normally is in some burrowing
quadrupeds having nearly similar habits with the Tuco-tuco?

In as far then as it is admitted as probable that the
effects of disuse (together with occasional true and sudden abortions
during the embryonic period) would cause a part to be less developed,
and finally to become abortive and useless; then during the infinitely
numerous changes of habits in the many descendants from a common stock,
we might fairly have expected that cases of organs becom<ing> abortive
would have been numerous. The preservation of the stump of the tail, as
usually happens when an animal is born tailless, we can only explain by
the strength of the hereditary principle and by the period in embryo
when affected1: but on the theory of disuse gradually
obliterating a part, we can see, according to the principles explained
in the last chapter (viz. of hereditariness at corresponding periods of
life2, together with the use and disuse of the part in
question not being brought into play in early or embryonic life), that
organs or parts would tend not to be utterly obliterated, but to be
reduced to that state in which they existed in early embryonic life.
Owen often speaks of a part in a full-grown animal being in an
"embryonic condition." Moreover we can thus see why abortive organs are
most developed at an early period of life. Again, by gradual selection,
we can see how an organ rendered abortive in its primary use might be
converted to other purposes; a duck's wing might come to serve for a
fin, as does that of the penguin; an abortive bone might come to serve,
by the slow increment and change of place in the muscular fibres, as a
fulcrum for a new series of muscles; the pistil3 of the
marigold might become abortive as a reproductive part, but be continued
in its function of sweeping the pollen out of the anthers; for if in

1 These words seem to have been
inserted as an afterthought.

2Origin, Ed. i. p.
444, vi. p. 611.

3 This and similar cases occur
in the Origin, Ed. i. p. 452, vi. p. 621.

this latter respect the abortion had not been checked by
selection, the species must have become extinct from the pollen
remaining enclosed in the capsules of the anthers.

Finally then I must repeat that these wonderful facts of
organs formed with traces of exquisite care, but now either absolutely
useless or adapted to ends wholly different from their ordinary end,
being present and forming part of the structure of almost every
inhabitant of this world, both in long-past and present times—being
best developed and often only discoverable at a very early embryonic
period, and being full of signification in arranging the long series of
organic beings in a natural system—these
wonderful facts not only receive a simple explanation on the theory of
long-continued selection of many species from a few common
parent-stocks, but necessarily follow from this theory. If this theory
be rejected, these facts remain quite inexplicable; without indeed we
rank as an explanation such loose metaphors as that of De Candolle's1,
in which the kingdom of nature is compared to a well-covered table, and
the abortive organs are considered as put in for the sake of symmetry!

1 The metaphor of the dishes is
given in the Essay of 1842, p. 47, note 3.

I WILL now recapitulate the course of this work, more
fully with respect to the former parts, and briefly <as to> the latter.
In the first chapter we have seen that most, if not all, organic
beings, when taken by man out of their natural condition, and bred
during several generations, vary; that is variation is partly due to
the direct effect of the new external influences, and partly to the
indirect effect on the reproductive system rendering the organization
of the offspring in some degree plastic. Of the variations thus
produced, man when uncivilised naturally preserves the life, and
therefore unintentionally breeds from those individuals most useful to
him in his different states: when even semi-civilised, he intentionally
separates and breeds from such individuals. Every part of the structure
seems occasionally to vary in a very slight degree, and the extent to
which all kinds of peculiarities in mind and body, when congenital and
when slowly acquired either from external influences, from exercise, or
from disuse <are inherited> is truly wonderful. When several breeds are
once formed, then crossing is the most fertile source of new breeds1.
Variation

1 Compare however Darwin's later
view:—"The possibility of making distinct races by crossing has been
greatly exaggerated," Origin, Ed. i. p. 20, vi. p. 23. The
author's change of opinion was no doubt partly due to his experience in
breeding pigeons.

must be ruled, of course, by the health of the new race,
by the tendency to return to the ancestral forms, and by unknown laws
determining the proportional increase and symmetry of the body. The
amount of variation, which has been effected under domestication, is
quite unknown in the majority of domestic beings.

In the second chapter it was shown that wild organisms
undoubtedly vary in some slight degree: and that the kind of variation,
though much less in degree, is similar to that of domestic organisms.
It is highly probable that every organic being, if subjected during
several generations to new and varying conditions, would vary. It is
certain that organisms, living in an isolated country which
is undergoing geological changes, must in the course of time be so
subjected to new conditions; moreover an organism, when by chance
transported into a new station, for instance into an island, will often
be exposed to new conditions, and be surrounded by a new series of
organic beings. If there were no power at work selecting every slight
variation, which opened new sources of subsistence to a being thus
situated, the effects of crossing, the chance of death and the constant
tendency to reversion to the old parent-form, would prevent the
production of new races. If there were any selective agency at work, it
seems impossible to assign any limit1 to the complexity and
beauty of the adaptive structures, which might thus be
produced: for certainly the limit of possible variation of organic
beings, either in a wild or domestic state, is not known.

It was then shown, from the geometrically increasing
tendency of each species to multiply (as evidenced from what we know of
mankind and

of other animals when favoured by circumstances), and from
the means of subsistence of each species on an average remaining
constant, that during some part of the life of each, or during every
few generations, there must be a severe struggle for existence; and
that less than a grain1 in the balance will determine which
individuals shall live and which perish. In a country, therefore,
undergoing changes, and cut off from the free immigration of species
better adapted to the new station and conditions, it cannot be doubted
that there is a most powerful means of selection, tending to
preserve even the slightest variation, which aided the subsistence or
defence of those organic beings, during any part of their whole
existence, whose organization had been rendered plastic. Moreover, in
animals in which the sexes are distinct, there is a sexual struggle, by
which the most vigorous, and consequently the best adapted, will
oftener procreate their kind.

A new race thus formed by natural selection would be
undistinguishable from a species. For comparing, on the one hand, the
several species of a genus, and on the other hand several domestic
races from a common stock, we cannot discriminate them by the amount of
external difference, but only, first, by domestic races not remaining
so constant or being so "true" as species are; and secondly by races
always producing fertile offspring when crossed. And it was then shown
that a race naturally selected—from
the variation being slower—from
the selection steadily leading towards the same ends2, and
from every new slight change in structure being adapted (as is implied
by its selec-

1 "A grain in the balance will
determine which individual shall live and which shall die," Origin,
Ed. i. p. 467, vi. p. 642. A similar statement occurs in the 1842
Essay, p. 8, note 3.

2 Thus according to the author
what is now known as orthogenesis is due to selection.

tion) to the new conditions and being fully exercised, and
lastly from the freedom from occasional crosses with other species,
would almost necessarily be "truer" than a race selected by ignorant or
capricious and short-lived man. With respect to the sterility of
species when crossed, it was shown not to be a universal character, and
when present to vary in degree: sterility also was shown probably to
depend less on external than on constitutional differences. And it was
shown that when individual animals and plants are placed under new
conditions, they become, without losing their healths, as sterile, in
the same manner and to the same degree, as hybrids; and it is therefore
conceivable that the cross-bred offspring between two species, having
different constitutions, might have its constitution affected in the
same peculiar manner as when an individual animal or plant is placed
under new conditions. Man in selecting domestic races has little wish
and still less power to adapt the whole frame to new conditions; in
nature, however, where each species survives by a struggle against
other species and external nature, the result must be very different.

Races descending from the same stock were then compared
with species of the same genus, and they were found to present some
striking analogies. The offspring also of races when crossed, that is
mongrels, were compared with the cross-bred offspring of species, that
is hybrids, and they were found to resemble each other in all their
characters, with the one exception of sterility, and even this, when
present, often becomes after some generations variable in degree. The
chapter was summed up, and it was shown that no ascertained limit to
the amount of variation is known; or could be predicted with due time
and changes of condition granted. It was then admitted that although
the production of new races, undistinguishable from

true species, is probable, we must look to the relations
in the past and present geographical distribution of the infinitely
numerous beings, by which we are surrounded—to
their affinities and to their structure—for
any direct evidence.

In the third chapter the inheritable variations in the
mental phenomena of domestic and of wild organic beings were
considered. It was shown that we are not concerned in this work with
the first origin of the leading mental qualities; but that tastes,
passions, dispositions, consensual movements, and habits all became,
either congenitally or during mature life, modified and were inherited.
Several of these modified habits were found to correspond in every
essential character with true instincts, and they were found to follow
the same laws. Instincts and dispositions &c. are fully as
important to the preservation and increase of a species as its
corporeal structure; and therefore the natural means of selection would
act on and modify them equally with corporeal structures. This being
granted, as well as the proposition that mental phenomena are variable,
and that the modifications are inheritable, the possibility of the
several most complicated instincts being slowly acquired was
considered, and it was shown from the very imperfect series in the
instincts of the animals now existing, that we are not justified in prima
facie rejecting a theory of the common descent of allied
organisms from the difficulty of imagining the transitional stages in
the various now most complicated and wonderful instincts. We were thus
led on to consider the same question with respect both to highly
complicated organs, and to the aggregate of several such organs, that
is individual organic beings; and it was shown, by the same method of
taking the existing most imperfect series, that we ought not at once to
reject the theory, because we cannot trace the transitional

stages in such organs, or conjecture the transitional
habits of such individual species.

In the Second Part1 the direct evidence of
allied forms having descended from the same stock was discussed. It was
shown that this theory requires a long series of intermediate forms
between the species and groups in the same classes—forms
not directly intermediate between existing species, but intermediate
with a common parent. It was admitted that if even all the preserved
fossils and existing species were collected, such a series would be far
from being formed; but it was shown that we have not good evidence
that the oldest known deposits are contemporaneous with the first
appearance of living beings; or that the several subsequent formations
are nearly consecutive; or that any one formation preserves a nearly
perfect fauna of even the hard marine organisms, which lived in that
quarter of the world. Consequently, we have no reason to suppose that
more than a small fraction of the organisms which have lived at any one
period have ever been preserved; and hence that we ought not to expect
to discover the fossilised sub-varieties between any two species. On
the other hand, the evidence, though extremely imperfect, drawn from
fossil remains, as far as it does go, is in favour of such a series of
organisms having existed as that required. This want of evidence of the
past existence of almost infinitely numerous intermediate forms, is, I
conceive, much the weightiest difficulty2 on the theory of
common descent; but I must think that this is due to ignorance
necessarily resulting from the imperfection of all geological records.

1 Part II begins with Ch. IV.
See the Introduction, where the absence of division into two parts (in
the Origin) is discussed.

2 In the recapitulation in the
last chapter of the Origin, Ed. i. p. 475, vi. p. 651, the
author does not insist on this point as the weightiest difficulty,
though he does so in Ed. i. p. 299. It is possible that he had come to
think less of the difficulty in question: this was certainly the case
when he wrote the 6th edition, see p. 438.

In the fifth chapter it was shown that new species
gradually1 appear, and that the old ones gradually
disappear, from the earth; and this strictly accords with our theory.
The extinction of species seems to be preceded by their rarity; and if
this be so, no one ought to feel more surprise at a species being
exterminated than at its being rare. Every species which is not
increasing in number must have its geometrical tendency to increase
checked by some agency seldom accurately perceived by us. Each slight
increase in the power of this unseen checking agency would cause a
corresponding decrease in the average numbers of that species, and the
species would become rarer: we feel not the least surprise at one
species of a genus being rare and another abundant; why then should we
be surprised at its extinction, when we have good reason to believe
that this very rarity is its regular precursor and cause.

In the sixth chapter the leading facts in the geographical
distribution of organic beings were considered—namely,
the dissimilarity in areas widely and effectually separated, of the
organic beings being exposed to very similar conditions (as for
instance, within the tropical forests of Africa and America, or on the
volcanic islands adjoining them). Also the striking similarity and
general relations of the inhabitants of the same great continents,
conjoined with a lesser degree of dissimilarity in the inhabitants
living on opposite sides of the barriers intersecting it—whether
or not these opposite sides are exposed to similar conditions. Also the
dissimilarity, though in a still lesser degree, in the inhabitants of
different islands in the same archipelago, together with their
similarity taken as a

1 <The following words:> The
fauna changes singly <were inserted by the author, apparently to
replace a doubtful erasure>.

whole with the inhabitants of the nearest continent,
whatever its character may be. Again, the peculiar relations of Alpine
floras; the absence of mammifers on the smaller isolated islands; and
the comparative fewness of the plants and other organisms on islands
with diversified stations; the connection between the possibility of
occasional transportal from one country to another, with an affinity,
though not identity, of the organic beings inhabiting them. And lastly,
the clear and striking relations between the living and the extinct in
the same great divisions of the world; which relation, if we look very
far backward, seems to die away. These facts, if we bear in mind the
geological changes in progress, all simply follow from the proposition
of allied organic beings having lineally descended from common
parent-stocks. On the theory of independent creations they must remain,
though evidently connected together, inexplicable and disconnected.

In the seventh chapter, the relationship or grouping of
extinct and recent species; the appearance and disappearance of groups;
the ill-defined objects of the natural classification, not depending on
the similarity of organs physiologically important, not being
influenced by adaptive or analogical characters, though these often
govern the whole economy of the individual, but depending on any
character which varies least, and especially on the forms through which
the embryo passes, and, as was afterwards shown, on the presence of
rudimentary and useless organs. The alliance between the nearest
species in distinct groups being general and not especial;
the close similarity in the rules and objects in classifying domestic
races and true species. All these facts were shown to follow on the
natural system being a genealogical system.

In the eighth chapter, the unity of structure throughout
large groups, in species adapted to the

most different lives, and the wonderful metamorphosis
(used metaphorically by naturalists) of one part or organ into another,
were shown to follow simply on new species being produced by the
selection and inheritance of successive small changes of
structure. The unity of type is wonderfully manifested by the
similarity of structure, during the embryonic period, in the species of
entire classes. To explain this it was shown that the different races
of our domestic animals differ less, during their young state, than
when full grown; and consequently, if species are produced like races,
the same fact, on a greater scale, might have been expected to hold
good with them. This remarkable law of nature was attempted to be
explained through establishing, by sundry facts, that slight variations
originally appear during all periods of life, and that when inherited
they tend to appear at the corresponding period of life; according to
these principles, in several species descended from the same
parent-stock, their embryos would almost necessarily much more closely
resemble each other than they would in their adult state. The
importance of these embryonic resemblances, in making out a natural or
genealogical classification, thus becomes at once obvious. The
occasional greater simplicity of structure in the mature animal than in
the embryo; the gradation in complexity of the species in the great
classes; the adaptation of the larvæ of animals to independent powers
of existence; the immense difference in certain animals in their larval
and mature states, were all shown on the above principles to present no
difficulty.

In the <ninth> chapter, the frequent and almost general
presence of organs and parts, called by naturalists abortive or
rudimentary, which, though formed with exquisite care, are generally
absolutely useless <was considered>. <These structures,> though

sometimes applied to uses not normal,—which cannot be
considered as mere representative parts, for they are sometimes capable
of performing their proper function,—which are always best developed,
and sometimes only developed, during a very early period of life,—and
which are of admitted high importance in classification,—were shown to
be simply explicable on our theory of common descent.

Why do we wish to reject
the theory of common descent?

Thus have many general facts, or laws, been included under
one explanation; and the difficulties encountered are those which would
naturally result from our acknowledged ignorance. And why should we not
admit this theory of descent1? Can it be shown that organic
beings in a natural state are all absolutely invariable?Can
it be said that the limit of variation or the number of
varieties capable of being formed under domestication are known? Can
any distinct line be drawn between a race and a species? To
these three questions we may certainly answer in the negative. As long
as species were thought to be divided and defined by an impassable
barrier of sterility, whilst we were ignorant of geology, and
imagined that the world was of short duration, and the number
of its past inhabitants few, we were justified in assuming individual
creations, or in saying with Whewell that the beginnings of all things
are hidden from man. Why then do we feel so strong an inclination to
reject this theory—especially
when the actual case of any two species, or even of any two races, is
adduced—and one is asked,
have these two originally descended from the same parent womb? I
believe it is because we are

1 This question forms the
subject of what is practically a section of the final chapter of the Origin (Ed. i. p. 480, vi. p. 657).

always slow in admitting any great change of which we do
not see the intermediate steps. The mind cannot grasp the full meaning
of the term of a million or hundred million years, and cannot
consequently add up and perceive the full effects of small successive
variations accumulated during almost infinitely many generations. The
difficulty is the same with that which, with most geologists, it has
taken long years to remove, as when Lyell propounded that great valleys1 were hollowed out [and long lines of inland cliffs had been formed] by
the slow action of the waves of the sea. A man may long view a grand
precipice without actually believing, though he may not deny it, that
thousands of feet in thickness of solid rock once extended over many
square miles where the open sea now rolls; without fully believing that
the same sea which he sees beating the rock at his feet has been the
sole removing power.

Shall we then allow that the three distinct species of
rhinoceros2 which separately inhabit Java and Sumatra and
the neighbouring mainland of Malacca were created, male and female, out
of the inorganic materials of these countries? Without any adequate
cause, as far as our reason serves, shall we say that they were merely,
from living near each other, created very like each other, so as to
form a section of the genus dissimilar from the African section, some
of the species of which section inhabit very similar and some very
dissimilar stations? Shall we say that without any apparent cause they
were created on the same generic type with the ancient woolly
rhinoceros of Siberia and of the other species which formerly inhabited
the same main division of the world: that they were created, less

1 Origin, Ed. i. p.
481, vi. p. 659.

2 The discussion on the three
species of Rhinoceros which also occurs in the Essay of
1842, p. 48, was omitted in Ch. XIV of the Origin, Ed. i.

and less closely related, but still with interbranching
affinities, with all the other living and extinct mammalia? That
without any apparant adequate cause their short necks should contain
the same number of vertebræ with the giraffe; that their thick legs
should be built on the same plan with those of the antelope, of the
mouse, of the hand of the monkey, of the wing of the bat, and of the
fin of the porpoise. That in each of these species the second bone of
their leg should show clear traces of two bones having been soldered
and united into one; that the complicated bones of their head should
become intelligible on the supposition of their having been formed of
three expanded vertebræ; that in the jaws of each when dissected young
there should exist small teeth which never come to the surface. That in
possessing these useless abortive teeth, and in other characters, these
three rhinoceroses in their embryonic state should much more closely
resemble other mammalia than they do when mature. And lastly, that in a
still earlier period of life, their arteries should run and branch as
in a fish, to carry the blood to gills which do not exist. Now these
three species of rhinoceros closely resemble each other; more closely
than many generally acknowledged races of our domestic animals; these
three species if domesticated would almost certainly vary, and races
adapted to different ends might be selected out of such variations. In
this state they would probably breed together, and their offspring
would possibly be quite, and probably in some degree, fertile; and in
either case, by continued crossing, one of these specific forms might
be absorbed and lost in another. I repeat, shall we then say that a
pair, or a gravid female, of each of these three species of rhinoceros,
were separately created with deceptive appearances of true
relationship, with the stamp of inutility on

some parts, and of conversion in other parts, out of the
inorganic elements of Java, Sumatra and Malacca? or have they
descended, like our domestic races, from the same parent-stock? For my
own part I could no more admit the former proposition than I could
admit that the planets move in their courses, and that a stone falls to
the ground, not through the intervention of the secondary and appointed
law of gravity, but from the direct volition of the Creator.

Before concluding it will be well to show, although this
has incidentally appeared, how far the theory of common descent can
legitimately be extended1. If we once admit that two true
species of the same genus can have descended from the same parent, it
will not be possible to deny that two species of two genera may also
have descended from a common stock. For in some families the genera
approach almost as closely as species of the same genus; and in some
orders, for instance in the monocotyledonous plants, the families run
closely into each other. We do not hesitate to assign a common origin
to dogs or cabbages, because they are divided into groups analogous to
the groups in nature. Many naturalists indeed admit that all groups are
artificial; and that they depend entirely on the extinction of
intermediate species. Some naturalists, however, affirm that though
driven from considering sterility as the characteristic of species,
that an entire incapacity to propagate together is the best evidence of
the existence of natural genera. Even if we put on one side the
undoubted fact that some species of the same genus

1 This corresponds to a
paragraph in the Origin, Ed. i. p. 483, vi. p. 662, where it
is assumed that animals have descended "from at most only four or five
progenitors, and plants from an equal or lesser number." In the Origin,
however, the author goes on, Ed. i. p. 484, vi. p. 663: "Analogy would
lead me one step further, namely, to the belief that all animals and
plants have descended from some one prototype."

will not breed together, we cannot possibly admit the
above rule, seeing that the grouse and pheasant (considered by some
good ornithologists as forming two families), the bull-finch and
canary-bird have bred together.

No doubt the more remote two species are from each other,
the weaker the arguments become in favour of their common descent. In
species of two distinct families the analogy, from the variation of
domestic organisms and from the manner of their intermarrying, fails;
and the arguments from their geographical distribution quite or almost
quite fails. But if we once admit the general principles of this work,
as far as a clear unity of type can be made out in groups of species,
adapted to play diversified parts in the economy of nature, whether
shown in the structure of the embryonic or mature being, and especially
if shown by a community of abortive parts, we are legitimately led to
admit their community of descent. Naturalists dispute how widely this
unity of type extends: most, however, admit that the vertebrata are
built on one type; the articulata on another; the mollusca on a third;
and the radiata on probably more than one. Plants also appear to fall
under three or four great types. On this theory, therefore, all the
organisms yet discovered are descendants of probably less
than ten parent-forms.

Conclusion.

My reasons have now been assigned for believing that
specific forms are not immutable creations1. The terms used
by naturalists of affinity, unity of type, adaptive characters, the
metamorphosis and

1 This sentence corresponds, not
to the final section of the Origin, Ed. i. p. 484, vi. p.
664, but rather to the opening words of the section already referred to
(Origin, Ed. i. p. 480, vi. p. 657).

abortion of organs, cease to be metaphorical expressions
and become intelligible facts. We no longer look at an organic being as
a savage does at a ship1 or other great work of art, as at a
thing wholly beyond his comprehension, but as a production that has a
history which we may search into. How interesting do all instincts
become when we speculate on their origin as hereditary habits, or as
slight congenital modifications of former instincts perpetuated by the
individuals so characterised having been preserved. When we look at
every complex instinct and mechanism as the summing up of a long
history of contrivances, each most useful to its possessor, nearly in
the same way as when we look at a great mechanical invention as the
summing up of the labour, the experience, the reason, and even the
blunders of numerous workmen. How interesting does the geographical
distribution of all organic beings, past and present, become as
throwing light on the ancient geography of the world. Geology loses
glory2 from the imperfection of its archives, but it gains
in the immensity of its subject. There is much grandeur in looking at
every existing organic being either as the lineal successor of some
form now buried under thousands of feet of solid rock, or as being the
co-descendant of that buried form of some more ancient and utterly lost
inhabitant of this world. It accords with what we know of the laws
impressed by the Creator3 on matter that the production and
extinction of forms should, like the birth and death of individuals, be

1 This simile occurs in the
Essay of 1842, p. 50, and in the Origin, Ed. i. p. 485, vi.
p. 665, i.e. in the final section of Ch. XIV (vi. Ch. XV).
In the MS. there is some erasure in pencil of which I
have taken no notice.

2 An almost identical sentence
occurs in the Origin, Ed. i. p. 487, vi. p. 667. The fine
prophecy (in the Origin, Ed. i. p. 486, vi. p. 666) on "the
almost untrodden field of inquiry" is wanting in the present Essay.

the result of secondary means. It is derogatory that the
Creator of countless Universes should have made by individual acts of
His will the myriads of creeping parasites and worms, which since the
earliest dawn of life have swarmed over the land and in the depths of
the ocean. We cease to be astonished1 that a group of
animals should have been formed to lay their eggs in the bowels and
flesh of other sensitive beings; that some animals should live by and
even delight in cruelty; that animals should be led away by false
instincts; that annually there should be an incalculable waste of the
pollen, eggs and immature beings; for we see in all this the inevitable
consequences of one great law, of the multiplication of organic beings
not created immutable. From death, famine, and the struggle for
existence, we see that the most exalted end which we are capable of
conceiving, namely, the creation of the higher animals2, has
directly proceeded. Doubtless, our first impression is to disbelieve
that any secondary law could produce infinitely numerous organic
beings, each characterised by the most exquisite workmanship and widely
extended adaptations: it at first accords better with our faculties to
suppose that each required the fiat of a Creator. There3 is
a [simple] grandeur in this view of life with its several powers of
growth, reproduction and of sensation, having been originally breathed
into matter under a few forms, perhaps into only one4,

1 A passage corresponding to
this occurs in the sketch of 1842, p. 51, but not in the last chapter
of the Origin.

2This sentence occurs
in an almost identical form in the Origin, Ed. i. p. 490, vi.
p. 669. It will be noted that man is not named though clearly referred
to. Elsewhere (Origin, Ed. i. p. 488) the author is bolder and
writes "Light will be thrown on the origin of man and his history." In
Ed. vi. p. 668, he writes "Much light &c."

3 For the history of this
sentence (with which the Origin of Species closes) see the
Essay of 1842, p. 52, note 2: also the concluding pages of the
Introduction.

and that whilst this planet has gone cycling onwards
according to the fixed laws of gravity and whilst land and water have
gone on replacing each other—that
from so simple an origin, through the selection of infinitesimal
varieties, endless forms most beautiful and most wonderful have been
evolved.

Classification, natural system of, 35, 199, 206, 208;
— by any constant character, 201;
— relation of, to
geography, 202;
— a law that members of two distinct groups resemble
each other not specifically but generally, 203, 212;
— of domestic
races, 204;
— rarity and extinction in relation to, 210

Organisms, gradual introduction
of new, 23, 144;
extinct related to, existing in the same manner as
representative existing ones to each other, 33, 192;
introduced,
beating indigenes, 153;
dependent on other organisms rather than on
physical surroundings, 185;
graduated complexity in the great classes,
227;
immature,

Species, representative, seen in going from N. to S. in a continent, 31 n., 156;
representative in archipelagoes, 187;
wide-ranging, 34 n., 146;
and varieties, difficulty of distinguishing, 4, 81, 197;
sterility of
crosses between, supposed to be criterion, 11, 134;
gradual appearance
and disappearance of, 23, 144;
survival of a few among many extinct, 146

Species, not created more than once, 168, 171, 191;
evolution of,
compared to birth of individuals, 150, 198, 253;
small number in New
Zealand as compared to the Cape, 171, 191;
persistence of, unchanged,
192, 199

Sports, 1, 58, 59, 64, 74, 95, 129, 186, 206, 224

Sterility, due to captivity, 12, 77 n.,
100;
of various plants, 13, 101;
of species when crossed, 11, 23, 96, 99, 103;
produced by conditions,
compared to sterility due to crossing, 101, 102

Struggle for life, 7, 91, 92, 148, 241

Subsidence, importance of, in relation to fossils, 25, 35 n., 195;
of
continent leading to isolation of organisms, 190;
not favourable to
birth of new species, 196